StringBuilder

java.lang.Object
- java.lang.StringBuilder

All Implemented Interfaces:

Serializable, Appendable, CharSequence
```
public final class StringBuilder
extends Object
implements Appendable, CharSequence, Serializable
```
A mutable sequence of characters. This class provides an API compatible with StringBuffer, but with no guarantee of synchronization. This class is designed for use as a drop-in replacement for StringBuffer in places where the string buffer was being used by a single thread (as is generally the case). Where possible, it is recommended that this class be used in preference to StringBuffer as it will be faster under most implementations.
The principal operations on a StringBuilder are the append and insert methods, which are overloaded so as to accept data of any type. Each effectively converts a given datum to a string and then appends or inserts the characters of that string to the string builder. The append method always adds these characters at the end of the builder; the insert method adds the characters at a specified point.
For example, if z refers to a string builder object whose current contents are " start", then the method call z.append("le") would cause the string builder to contain " startle", whereas z.insert(4, "le") would alter the string builder to contain "starlet".
In general, if sb refers to an instance of a StringBuilder, then sb.append(x) has the same effect as sb.insert(sb.length(), x). Every string builder has a capacity. As long as the length of the character sequence contained in the string builder does not exceed the capacity, it is not necessary to allocate a new internal buffer. If the internal buffer overflows, it is automatically made larger.
Instances of StringBuilder are not safe for use by multiple threads. If such synchronization is required then it is recommended that StringBuffer be used.

See Also:

StringBuffer, String, Serialized Form

Constructor Summary

Constructors
Constructor and Description
`StringBuilder()` Constructs a string builder with no characters in it and an initial capacity of 16 characters.
`StringBuilder(CharSequence seq)` Constructs a string builder that contains the same characters as the specified `CharSequence`.
`StringBuilder(int capacity)` Constructs a string builder with no characters in it and an initial capacity specified by the `capacity` argument.
`StringBuilder(String str)` Constructs a string builder initialized to the contents of the specified string.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`StringBuilder`	`append(boolean b)` Appends the string representation of the boolean argument to the sequence.
`StringBuilder`	`append(char c)` Appends the specified character to this `Appendable`.
`StringBuilder`	`append(char[] str)` Appends the string representation of the char array argument to this sequence.
`StringBuilder`	`append(char[] str, int offset, int len)` Appends the string representation of a subarray of the `char` array argument to this sequence.
`StringBuilder`	`append(CharSequence csq)` Appends the specified character sequence to this `Appendable`.
`StringBuilder`	`append(CharSequence s, int start, int end)` Appends a subsequence of the specified `CharSequence` to this sequence.
`StringBuilder`	`append(double d)` Appends the string representation of the double argument to this sequence.
`StringBuilder`	`append(float f)` Appends the string representation of the float argument to this sequence.
`StringBuilder`	`append(int i)` Appends the string representation of the int argument to this sequence.
`StringBuilder`	`append(long lng)` Appends the string representation of the long argument to this sequence.
`StringBuilder`	`append(Object obj)` Appends the string representation of the Object argument.
`StringBuilder`	`append(String str)` Appends the specified string to this character sequence.
`StringBuilder`	`append(StringBuffer sb)` Appends the specified `StringBuffer` to this sequence.
`int`	`capacity()` Returns the current capacity.
`char`	`charAt(int index)` Returns the `char` value in this sequence at the specified index.
`StringBuilder`	`delete(int start, int end)` Removes the characters in a substring of this sequence.
`StringBuilder`	`deleteCharAt(int index)` Removes the `char` at the specified position in this sequence.
`void`	`ensureCapacity(int minimumCapacity)` Ensures that the capacity is at least equal to the specified minimum.
`void`	`getChars(int srcBegin, int srcEnd, char[] dst, int dstBegin)` Characters are copied from this sequence into the destination character array `dst`.
`int`	`indexOf(String str)` Returns the index within this string of the first occurrence of the specified substring.
`int`	`indexOf(String str, int fromIndex)` Returns the index within this string of the first occurrence of the specified substring, starting at the specified index.
`StringBuilder`	`insert(int offset, boolean b)` Inserts the string representation of the `boolean` argument into this sequence.
`StringBuilder`	`insert(int offset, char c)` Inserts the string representation of the `char` argument into this sequence.
`StringBuilder`	`insert(int offset, char[] str)` Inserts the string representation of the `char` array argument into this sequence.
`StringBuilder`	`insert(int index, char[] str, int offset, int len)` Inserts the string representation of a subarray of the `str` array argument into this sequence.
`StringBuilder`	`insert(int dstOffset, CharSequence s)` Inserts the specified `CharSequence` into this sequence.
`StringBuilder`	`insert(int dstOffset, CharSequence s, int start, int end)` Inserts a subsequence of the specified `CharSequence` into this sequence.
`StringBuilder`	`insert(int offset, double d)` Inserts the string representation of the `double` argument into this sequence.
`StringBuilder`	`insert(int offset, float f)` Inserts the string representation of the `float` argument into this sequence.
`StringBuilder`	`insert(int offset, int i)` Inserts the string representation of the second `int` argument into this sequence.
`StringBuilder`	`insert(int offset, long l)` Inserts the string representation of the `long` argument into this sequence.
`StringBuilder`	`insert(int offset, Object obj)` Inserts the string representation of the `Object` argument into this character sequence.
`StringBuilder`	`insert(int offset, String str)` Inserts the string into this character sequence.
`int`	`lastIndexOf(String str)` Returns the index within this string of the rightmost occurrence of the specified substring.
`int`	`lastIndexOf(String str, int fromIndex)` Returns the index within this string of the last occurrence of the specified substring.
`int`	`length()` Returns the length (character count).
`StringBuilder`	`replace(int start, int end, String str)` Replaces the characters in a substring of this sequence with characters in the specified `String`.
`StringBuilder`	`reverse()` Causes this character sequence to be replaced by the reverse of the sequence.
`void`	`setCharAt(int index, char ch)` The character at the specified index is set to `ch`.
`void`	`setLength(int newLength)` Sets the length of the character sequence.
`CharSequence`	`subSequence(int start, int end)` Returns a new character sequence that is a subsequence of this sequence.
`String`	`substring(int start)` Returns a new `String` that contains a subsequence of characters currently contained in this character sequence.
`String`	`substring(int start, int end)` Returns a new `String` that contains a subsequence of characters currently contained in this sequence.
`String`	`toString()` Returns a string representation of the object.
`void`	`trimToSize()` Attempts to reduce storage used for the character sequence.

Methods inherited from class java.lang.Object
clone, equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - StringBuilder
```
public StringBuilder()
```
    Constructs a string builder with no characters in it and an initial capacity of 16 characters.
  - StringBuilder
```
public StringBuilder(CharSequence seq)
```
    Constructs a string builder that contains the same characters as the specified CharSequence. The initial capacity of the string builder is 16 plus the length of the CharSequence argument.
    
    Parameters:
    
    seq - the sequence to copy.
    
    Throws:
    
    NullPointerException - if seq is null
  - StringBuilder
```
public StringBuilder(int capacity)
```
    Constructs a string builder with no characters in it and an initial capacity specified by the capacity argument.
    
    Parameters:
    
    capacity - the initial capacity.
    
    Throws:
    
    NegativeArraySizeException - if the capacity argument is less than 0.
  - StringBuilder
```
public StringBuilder(String str)
```
    Constructs a string builder initialized to the contents of the specified string. The initial capacity of the string builder is 16 plus the length of the string argument.
    
    Parameters:
    
    str - the initial contents of the buffer.
    
    Throws:
    
    NullPointerException - if str is null
- Method Detail
  - append
```
public StringBuilder append(boolean b)
```
    Appends the string representation of the boolean argument to the sequence.
    The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(boolean), and the characters of that string were then appended to this character sequence.
    
    Parameters:
    
    b - a boolean
    
    Returns:
    
    a reference to this object.
  - append
```
public StringBuilder append(char c)
```
    Description copied from interface: Appendable
    
    Appends the specified character to this Appendable.
    
    Specified by:
    
    append in interface Appendable
    
    Parameters:
    
    c - The character to append
    
    Returns:
    
    A reference to this Appendable
  - append
```
public StringBuilder append(char[] str)
```
    Appends the string representation of the char array argument to this sequence.
    The characters of the array argument are appended, in order, to the contents of this sequence. The length of this sequence increases by the length of the argument.
    The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(char[]), and the characters of that string were then appended to this character sequence.
    
    Parameters:
    
    str - the characters to be appended.
    
    Returns:
    
    a reference to this object.
  - append
```
public StringBuilder append(char[] str,
                            int offset,
                            int len)
```
    Appends the string representation of a subarray of the char array argument to this sequence.
    Characters of the char array str, starting at index offset, are appended, in order, to the contents of this sequence. The length of this sequence increases by the value of len.
    The overall effect is exactly as if the arguments were converted to a string by the method String.valueOf(char[],int,int), and the characters of that string were then appended to this character sequence.
    
    Parameters:
    
    str - the characters to be appended.
    
    offset - the index of the first char to append.
    
    len - the number of chars to append.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    IndexOutOfBoundsException - if offset < 0 or len < 0 or offset+len > str.length
  - append
```
public StringBuilder append(@Nullable
                            CharSequence csq)
```
    Appends the specified character sequence to this Appendable.
    
    Specified by:
    
    append in interface Appendable
    
    Parameters:
    
    csq - The character sequence to append. If csq is null, then the four characters "null" are appended to this Appendable.
    
    Returns:
    
    A reference to this Appendable
  - append
```
public StringBuilder append(@Nullable
                            CharSequence s,
                            int start,
                            int end)
```
    Appends a subsequence of the specified CharSequence to this sequence.
    Characters of the argument s, starting at index start, are appended, in order, to the contents of this sequence up to the (exclusive) index end. The length of this sequence is increased by the value of end - start.
    Let n be the length of this character sequence just prior to execution of the append method. Then the character at index k in this character sequence becomes equal to the character at index k in this sequence, if k is less than n; otherwise, it is equal to the character at index k+start-n in the argument s.
    If s is null, then this method appends characters as if the s parameter was a sequence containing the four characters "null".
    
    Specified by:
    
    append in interface Appendable
    
    Parameters:
    
    s - the sequence to append.
    
    start - the starting index of the subsequence to be appended.
    
    end - the end index of the subsequence to be appended.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    IndexOutOfBoundsException - if start is negative, or start is greater than end or end is greater than s.length()
  - append
```
public StringBuilder append(double d)
```
    Appends the string representation of the double argument to this sequence.
    The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(double), and the characters of that string were then appended to this character sequence.
    
    Parameters:
    
    d - a double
    
    Returns:
    
    a reference to this object.
  - append
```
public StringBuilder append(float f)
```
    Appends the string representation of the float argument to this sequence.
    The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(float), and the characters of that string were then appended to this character sequence.
    
    Parameters:
    
    f - a float
    
    Returns:
    
    a reference to this object.
  - append
```
public StringBuilder append(int i)
```
    Appends the string representation of the int argument to this sequence.
    The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(int), and the characters of that string were then appended to this character sequence.
    
    Parameters:
    
    i - an int.
    
    Returns:
    
    a reference to this object.
  - append
```
public StringBuilder append(long lng)
```
    Appends the string representation of the long argument to this sequence.
    The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(long), and the characters of that string were then appended to this character sequence.
    
    Parameters:
    
    lng - a long.
    
    Returns:
    
    a reference to this object.
  - append
```
public StringBuilder append(@Nullable
                            Object obj)
```
    Appends the string representation of the Object argument.
    The overall effect is exactly as if the argument were converted to a string by the method String.valueOf(Object), and the characters of that string were then appended to this character sequence.
    
    Parameters:
    
    obj - an Object
    
    Returns:
    
    a reference to this object.
  - append
```
public StringBuilder append(@Nullable
                            String str)
```
    Appends the specified string to this character sequence.
    The characters of the String argument are appended, in order, increasing the length of this sequence by the length of the argument. If str is null, then the four characters "null" are appended.
    Let n be the length of this character sequence just prior to execution of the append method. Then the character at index k in the new character sequence is equal to the character at index k in the old character sequence, if k is less than n; otherwise, it is equal to the character at index k-n in the argument str.
    
    Parameters:
    
    str - a string.
    
    Returns:
    
    a reference to this object.
  - append
```
public StringBuilder append(@Nullable
                            StringBuffer sb)
```
    Appends the specified StringBuffer to this sequence.
    The characters of the StringBuffer argument are appended, in order, to this sequence, increasing the length of this sequence by the length of the argument. If sb is null, then the four characters "null" are appended to this sequence.
    Let n be the length of this character sequence just prior to execution of the append method. Then the character at index k in the new character sequence is equal to the character at index k in the old character sequence, if k is less than n; otherwise, it is equal to the character at index k-n in the argument sb.
    
    Parameters:
    
    sb - the StringBuffer to append.
    
    Returns:
    
    a reference to this object.
  - capacity
```
public int capacity()
```
    Returns the current capacity. The capacity is the amount of storage available for newly inserted characters, beyond which an allocation will occur.
    
    Returns:
    
    the current capacity
  - charAt
```
public char charAt(int index)
```
    Returns the char value in this sequence at the specified index. The first char value is at index 0, the next at index 1, and so on, as in array indexing.
    The index argument must be greater than or equal to 0, and less than the length of this sequence.
    
    Specified by:
    
    charAt in interface CharSequence
    
    Parameters:
    
    index - the index of the desired char value.
    
    Returns:
    
    the char value at the specified index.
    
    Throws:
    
    IndexOutOfBoundsException - if index is negative or greater than or equal to length().
  - delete
```
public StringBuilder delete(int start,
                            int end)
```
    Removes the characters in a substring of this sequence. The substring begins at the specified start and extends to the character at index end - 1 or to the end of the sequence if no such character exists. If start is equal to end, no changes are made.
    
    Parameters:
    
    start - The beginning index, inclusive.
    
    end - The ending index, exclusive.
    
    Returns:
    
    This object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if start is negative, greater than length(), or greater than end.
  - deleteCharAt
```
public StringBuilder deleteCharAt(int index)
```
    Removes the char at the specified position in this sequence. This sequence is shortened by one char.
    Note: If the character at the given index is a supplementary character, this method does not remove the entire character. If correct handling of supplementary characters is required, determine the number of chars to remove by calling Character.charCount(thisSequence.codePointAt(index)), where thisSequence is this sequence.
    
    Parameters:
    
    index - Index of char to remove
    
    Returns:
    
    This object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the index is negative or greater than or equal to length().
  - ensureCapacity
```
public void ensureCapacity(int minimumCapacity)
```
    Ensures that the capacity is at least equal to the specified minimum. If the current capacity is less than the argument, then a new internal array is allocated with greater capacity. The new capacity is the larger of:
    - The minimumCapacity argument.
    - Twice the old capacity, plus 2.
    If the minimumCapacity argument is nonpositive, this method takes no action and simply returns.
    Parameters:
    
    minimumCapacity - the minimum desired capacity.
  - getChars
```
public void getChars(int srcBegin,
                     int srcEnd,
                     char[] dst,
                     int dstBegin)
```
    Characters are copied from this sequence into the destination character array dst. The first character to be copied is at index srcBegin; the last character to be copied is at index srcEnd-1. The total number of characters to be copied is srcEnd-srcBegin. The characters are copied into the subarray of dst starting at index dstBegin and ending at index:
    dstbegin + (srcEnd - srcBegin) - 1
    Parameters:
    
    srcBegin - start copying at this offset.
    
    srcEnd - stop copying at this offset.
    
    dst - the array to copy the data into.
    
    dstBegin - offset into dst.
    
    Throws:
    
    NullPointerException - if dst is null.
    IndexOutOfBoundsException - if any of the following is true:
    
    srcBegin is negative
    dstBegin is negative
    the srcBegin argument is greater than the srcEnd argument.
    srcEnd is greater than this.length().
    dstBegin+srcEnd-srcBegin is greater than dst.length
  - indexOf
```
public int indexOf(String str)
```
    Returns the index within this string of the first occurrence of the specified substring. The integer returned is the smallest value k such that:
    this.toString().startsWith(str, k)
    is true.
    Parameters:
    
    str - any string.
    
    Returns:
    
    if the string argument occurs as a substring within this object, then the index of the first character of the first such substring is returned; if it does not occur as a substring, -1 is returned.
    
    Throws:
    
    NullPointerException - if str is null.
  - indexOf
```
public int indexOf(String str,
                   int fromIndex)
```
    Returns the index within this string of the first occurrence of the specified substring, starting at the specified index. The integer returned is the smallest value k for which:
    k >= Math.min(fromIndex, str.length()) && this.toString().startsWith(str, k)
    If no such value of k exists, then -1 is returned.
    Parameters:
    
    str - the substring for which to search.
    
    fromIndex - the index from which to start the search.
    
    Returns:
    
    the index within this string of the first occurrence of the specified substring, starting at the specified index.
    
    Throws:
    
    NullPointerException - if str is null.
  - insert
```
public StringBuilder insert(int offset,
                            boolean b)
```
    Inserts the string representation of the boolean argument into this sequence.
    The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(boolean), and the characters of that string were then inserted into this character sequence at the indicated offset.
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    
    Parameters:
    
    offset - the offset.
    
    b - a boolean.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int offset,
                            char c)
```
    Inserts the string representation of the char argument into this sequence.
    The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(char), and the character in that string were then inserted into this character sequence at the indicated offset.
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    
    Parameters:
    
    offset - the offset.
    
    c - a char.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    IndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int offset,
                            char[] str)
```
    Inserts the string representation of the char array argument into this sequence.
    The characters of the array argument are inserted into the contents of this sequence at the position indicated by offset. The length of this sequence increases by the length of the argument.
    The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(char[]), and the characters of that string were then inserted into this character sequence at the indicated offset.
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    
    Parameters:
    
    offset - the offset.
    
    str - a character array.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int index,
                            char[] str,
                            int offset,
                            int len)
```
    Inserts the string representation of a subarray of the str array argument into this sequence. The subarray begins at the specified offset and extends len chars. The characters of the subarray are inserted into this sequence at the position indicated by index. The length of this sequence increases by len char s.
    
    Parameters:
    
    index - position at which to insert subarray.
    
    str - A char array.
    
    offset - the index of the first char in subarray to be inserted.
    
    len - the number of chars in the subarray to be inserted.
    
    Returns:
    
    This object
    
    Throws:
    
    StringIndexOutOfBoundsException - if index is negative or greater than length(), or offset or len are negative, or (offset+len) is greater than str.length.
  - insert
```
public StringBuilder insert(int dstOffset,
                            @Nullable
                            CharSequence s)
```
    Inserts the specified CharSequence into this sequence.
    The characters of the CharSequence argument are inserted, in order, into this sequence at the indicated offset, moving up any characters originally above that position and increasing the length of this sequence by the length of the argument s.
    The result of this method is exactly the same as if it were an invocation of this object's insert(dstOffset, s, 0, s.length()) method.
    If s is null, then the four characters "null" are inserted into this sequence.
    
    Parameters:
    
    dstOffset - the offset.
    
    s - the sequence to be inserted
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    IndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int dstOffset,
                            @Nullable
                            CharSequence s,
                            int start,
                            int end)
```
    Inserts a subsequence of the specified CharSequence into this sequence.
    The subsequence of the argument s specified by start and end are inserted, in order, into this sequence at the specified destination offset, moving up any characters originally above that position. The length of this sequence is increased by end - start.
    The character at index k in this sequence becomes equal to:
    - the character at index k in this sequence, if k is less than dstOffset
    - the character at index k+start-dstOffset in the argument s, if k is greater than or equal to dstOffset but is less than dstOffset+end-start
    - the character at index k-(end-start) in this sequence, if k is greater than or equal to dstOffset+end-start
    The dstOffset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    The start argument must be nonnegative, and not greater than end.
    The end argument must be greater than or equal to start, and less than or equal to the length of s.
    If s is null, then this method inserts characters as if the s parameter was a sequence containing the four characters "null".
    Parameters:
    
    dstOffset - the offset in this sequence.
    
    s - the sequence to be inserted.
    
    start - the starting index of the subsequence to be inserted.
    
    end - the end index of the subsequence to be inserted.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    IndexOutOfBoundsException - if dstOffset is negative or greater than this.length(), or start or end are negative, or start is greater than end or end is greater than s.length()
  - insert
```
public StringBuilder insert(int offset,
                            double d)
```
    Inserts the string representation of the double argument into this sequence.
    The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(double), and the characters of that string were then inserted into this character sequence at the indicated offset.
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    
    Parameters:
    
    offset - the offset.
    
    d - a double.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int offset,
                            float f)
```
    Inserts the string representation of the float argument into this sequence.
    The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(float), and the characters of that string were then inserted into this character sequence at the indicated offset.
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    
    Parameters:
    
    offset - the offset.
    
    f - a float.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int offset,
                            int i)
```
    Inserts the string representation of the second int argument into this sequence.
    The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(int), and the characters of that string were then inserted into this character sequence at the indicated offset.
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    
    Parameters:
    
    offset - the offset.
    
    i - an int.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int offset,
                            long l)
```
    Inserts the string representation of the long argument into this sequence.
    The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(long), and the characters of that string were then inserted into this character sequence at the indicated offset.
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    
    Parameters:
    
    offset - the offset.
    
    l - a long.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int offset,
                            Object obj)
```
    Inserts the string representation of the Object argument into this character sequence.
    The overall effect is exactly as if the second argument were converted to a string by the method String.valueOf(Object), and the characters of that string were then inserted into this character sequence at the indicated offset.
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    
    Parameters:
    
    offset - the offset.
    
    obj - an Object.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the offset is invalid.
  - insert
```
public StringBuilder insert(int offset,
                            @Nullable
                            String str)
```
    Inserts the string into this character sequence.
    The characters of the String argument are inserted, in order, into this sequence at the indicated offset, moving up any characters originally above that position and increasing the length of this sequence by the length of the argument. If str is null, then the four characters "null" are inserted into this sequence.
    The character at index k in the new character sequence is equal to:
    - the character at index k in the old character sequence, if k is less than offset
    - the character at index k-offset in the argument str, if k is not less than offset but is less than offset+str.length()
    - the character at index k-str.length() in the old character sequence, if k is not less than offset+str.length()
    The offset argument must be greater than or equal to 0, and less than or equal to the length of this sequence.
    Parameters:
    
    offset - the offset.
    
    str - a string.
    
    Returns:
    
    a reference to this object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if the offset is invalid.
  - lastIndexOf
```
public int lastIndexOf(String str)
```
    Returns the index within this string of the rightmost occurrence of the specified substring. The rightmost empty string "" is considered to occur at the index value this.length(). The returned index is the largest value k such that
    this.toString().startsWith(str, k)
    is true.
    Parameters:
    
    str - the substring to search for.
    
    Returns:
    
    if the string argument occurs one or more times as a substring within this object, then the index of the first character of the last such substring is returned. If it does not occur as a substring, -1 is returned.
    
    Throws:
    
    NullPointerException - if str is null.
  - lastIndexOf
```
public int lastIndexOf(String str,
                       int fromIndex)
```
    Returns the index within this string of the last occurrence of the specified substring. The integer returned is the largest value k such that:
    k <= Math.min(fromIndex, str.length()) && this.toString().startsWith(str, k)
    If no such value of k exists, then -1 is returned.
    Parameters:
    
    str - the substring to search for.
    
    fromIndex - the index to start the search from.
    
    Returns:
    
    the index within this sequence of the last occurrence of the specified substring.
    
    Throws:
    
    NullPointerException - if str is null.
  - length
```
public int length()
```
    Returns the length (character count).
    
    Specified by:
    
    length in interface CharSequence
    
    Returns:
    
    the length of the sequence of characters currently represented by this object
  - replace
```
public StringBuilder replace(int start,
                             int end,
                             String str)
```
    Replaces the characters in a substring of this sequence with characters in the specified String. The substring begins at the specified start and extends to the character at index end - 1 or to the end of the sequence if no such character exists. First the characters in the substring are removed and then the specified String is inserted at start. (This sequence will be lengthened to accommodate the specified String if necessary.)
    
    Parameters:
    
    start - The beginning index, inclusive.
    
    end - The ending index, exclusive.
    
    str - String that will replace previous contents.
    
    Returns:
    
    This object.
    
    Throws:
    
    StringIndexOutOfBoundsException - if start is negative, greater than length(), or greater than end.
  - reverse
```
public StringBuilder reverse()
```
    Causes this character sequence to be replaced by the reverse of the sequence. Let n be the character length of this character sequence (not the length in char values) just prior to execution of the reverse method. Then the character at index k in the new character sequence is equal to the character at index n-k-1 in the old character sequence.
    
    Returns:
    
    a reference to this object.
  - setCharAt
```
public void setCharAt(int index,
                      char ch)
```
    The character at the specified index is set to ch. This sequence is altered to represent a new character sequence that is identical to the old character sequence, except that it contains the character ch at position index.
    The index argument must be greater than or equal to 0, and less than the length of this sequence.
    
    Parameters:
    
    index - the index of the character to modify.
    
    ch - the new character.
    
    Throws:
    
    IndexOutOfBoundsException - if index is negative or greater than or equal to length().
    
    See Also:
    
    length()
  - setLength
```
public void setLength(int newLength)
```
    Sets the length of the character sequence. The sequence is changed to a new character sequence whose length is specified by the argument. For every nonnegative index k less than newLength, the character at index k in the new character sequence is the same as the character at index k in the old sequence if k is less than the length of the old character sequence; otherwise, it is the null character '\u0000'. In other words, if the newLength argument is less than the current length, the length is changed to the specified length.
    If the newLength argument is greater than or equal to the current length, sufficient null characters ('\u0000') are appended so that length becomes the newLength argument.
    The newLength argument must be greater than or equal to 0.
    
    Parameters:
    
    newLength - the new length
    
    Throws:
    
    IndexOutOfBoundsException - if the newLength argument is negative.
    
    See Also:
    
    length()
  - subSequence
```
public CharSequence subSequence(int start,
                                int end)
```
    Returns a new character sequence that is a subsequence of this sequence. This method is provided so that this class can implement the CharSequence interface.
    
    Specified by:
    
    subSequence in interface CharSequence
    
    Parameters:
    
    start - the start index, inclusive.
    
    end - the end index, exclusive.
    
    Returns:
    
    the specified subsequence.
    
    Throws:
    
    IndexOutOfBoundsException - if start or end are negative, if end is greater than length(), or if start is greater than end
  - substring
```
public String substring(int start)
```
    Returns a new String that contains a subsequence of characters currently contained in this character sequence. The substring begins at the specified index and extends to the end of this sequence.
    
    Parameters:
    
    start - The beginning index, inclusive.
    
    Returns:
    
    The new string.
    
    Throws:
    
    StringIndexOutOfBoundsException - if start is less than zero, or greater than the length of this object.
  - substring
```
public String substring(int start,
                        int end)
```
    Returns a new String that contains a subsequence of characters currently contained in this sequence. The substring begins at the specified start and extends to the character at index end - 1.
    
    Parameters:
    
    start - The beginning index, inclusive.
    
    end - The ending index, exclusive.
    
    Returns:
    
    The new string.
    
    Throws:
    
    StringIndexOutOfBoundsException - if start or end are negative or greater than length(), or start is greater than end.
  - toString
```
public String toString()
```
    Description copied from class: Object
    Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.
    The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:
    getClass().getName() + '@' + Integer.toHexString(hashCode())
    Specified by:
    
    toString in interface CharSequence
    
    Overrides:
    
    toString in class Object
    
    Returns:
    
    a string representation of the object.
  - trimToSize
```
public void trimToSize()
```
    Attempts to reduce storage used for the character sequence. If the buffer is larger than necessary to hold its current sequence of characters, then it may be resized to become more space efficient. Calling this method may, but is not required to, affect the value returned by a subsequent call to the capacity() method.

Class StringBuilder

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

StringBuilder

StringBuilder

StringBuilder

StringBuilder

Method Detail

append

append

append

append

append

append

append

append

append

append

append

append

append

capacity

charAt

delete

deleteCharAt

ensureCapacity

getChars

indexOf

indexOf

insert

insert

insert

insert

insert

insert

insert

insert

insert

insert

insert

insert

lastIndexOf

lastIndexOf

length

replace

reverse

setCharAt

setLength

subSequence

substring

substring

toString

trimToSize