ej.mwt.stylesheet.selector

Class FirstChildSelector

java.lang.Object

ej.mwt.stylesheet.selector.FirstChildSelector

All Implemented Interfaces:

Selector

public class FirstChildSelector
extends Object
implements Selector

A first child selector selects by checking if a widget is the first child of its parent.

Equivalent to :first-child selector in CSS. Its specificity is (0,0,1,0).

See Also:

Widget.getParent(), SelectorHelper

Field Summary

Fields

Modifier and Type	Field and Description
static FirstChildSelector	FIRST_CHILD_SELECTOR First child selector singleton to avoid creating several ones.

Constructor Summary

Constructors

Constructor and Description
FirstChildSelector()

Method Summary

Modifier and Type	Method and Description
boolean	appliesToWidget(Widget widget) Checks whether or not this selector applies to the given widget.
boolean	equals(Object obj) Indicates whether some other object is "equal to" this one.
int	getSpecificity() Returns the specificity of this selector.
int	hashCode() Returns a hash code value for the object.

Methods inherited from class java.lang.Object

clone, getClass, notify, notifyAll, toString, wait, wait, wait

Field Detail

FIRST_CHILD_SELECTOR

public static final FirstChildSelector FIRST_CHILD_SELECTOR

First child selector singleton to avoid creating several ones.

Constructor Detail

FirstChildSelector

public FirstChildSelector()

Method Detail

appliesToWidget

public boolean appliesToWidget(Widget widget)

Description copied from interface: Selector

Checks whether or not this selector applies to the given widget.

Specified by:

appliesToWidget in interface Selector

Parameters:

widget - the widget to test.

Returns:

true if this selectors applies to the given widget, false otherwise.

getSpecificity

public int getSpecificity()

Description copied from interface: Selector

Returns the specificity of this selector.

The specificity allows to determine in which order the rules of a stylesheet should be applied.

A specificity is composed of four numbers (defined by CSS2 specification):

• count 1 if the declaration is from is a 'style' attribute rather than a rule with a selector, 0 otherwise (= a)
• count the number of ID attributes in the selector (= b)
• count the number of other attributes and pseudo-classes in the selector (= c)
• count the number of widget names and pseudo-widgets in the selector (= d)

Concatenating the four numbers a-b-c-d (in a number system with a large base) gives the specificity. In this implementation, each number is stored on a byte in an integer. SelectorHelper provides a method to compute the specificity of a selector.

Specified by:

getSpecificity in interface Selector

Returns:

the specificity of this selector.

equals

public boolean equals(@Nullable
                      Object obj)

Description copied from class: Object

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

• It is reflexive: for any non-null reference value x, x.equals(x) should return true.
• It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
• It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
• It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
• For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Specified by:

equals in interface Selector

Overrides:

equals in class Object

Parameters:

obj - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), HashMap

hashCode

public int hashCode()

Description copied from class: Object

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

The general contract of hashCode is:

• Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
• If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
• It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java^TM programming language.)

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)