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Chapter 10 |  |
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Chapter 10 | |
Contents:
The package java.lang contains classes and interfaces that are essential to the Java language. These include:
Because the classes in the java.lang package are so essential, the java.lang package is implicitly imported by every Java source file. In other words, you can refer to all of the classes and interfaces in java.lang using their simple names.
Figure 10.1 shows the class hierarchy for the java.lang package.
java.lang.Boolean
java.lang.Object
None
java.io.Serializable
JDK 1.0 or later
The Boolean class provides an object wrapper for a boolean value. This is useful when you need to treat a boolean value as an object. For example, there are a number of utility methods that take a reference to an Object as one of their arguments. You cannot specify a boolean value for one of these arguments, but you can provide a reference to a Boolean object that encapsulates the boolean value. Furthermore, as of JDK 1.1, the Boolean class is necessary to support the Reflection API and class literals.
![[Graphic: Figure 10-1]](./figs/jlrf1001.gif)
public final class java.lang.Boolean {
// Constants
public final static Boolean FALSE;
public final static Boolean TRUE;
public final static Class TYPE; // New in 1.1
// Constructors
public Boolean(boolean value);
public Boolean(String s);
// Class Methods
public static boolean getBoolean(String name);
public static Boolean valueOf(String s);
// Instance Methods
public boolean booleanValue();
public boolean equals(Object obj);
public int hashCode();
public String toString();
}
A constant Boolean object that has the value true.
A constant Boolean object that has the value false.
New as of JDK 1.1
The Class object that represents the type boolean. It is always true that Boolean.TYPE == boolean.class.
The boolean value to be made into a Boolean object.
Constructs a Boolean object with the given value.
The string to be made into a Boolean object.
Constructs a Boolean object with the value specified by the given string. If the string equals 'true' (ignoring case), the value of the object is true; otherwise it is false.
The name of a system property.
The boolean value of the system property.
This methods retrieves the boolean value of a named system property.
The string to be made into a Boolean object.
A Boolean object with the value specified by the given string.
This method returns a Boolean object with the value true if the string equals "true" (ignoring case); otherwise the value of the object is false.
The boolean value contained by the object.
The object to be compared with this object.
true if the objects are equal; false if they are not.
Object.equals()
This method returns true if obj is an instance of Boolean, and it contains the same value as the object this method is associated with.
A hashcode based on the boolean value of the object.
Object.hashCode()
"true" if the value of the object is true; "false" otherwise.
Object.toString()
This method returns a string representation of the Boolean object.
|
Method |
Inherited From |
Method |
Inherited From |
|---|---|---|---|
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clone() |
Object |
finalize() |
Object |
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getClass() |
Object |
notify() |
Object |
|
notifyAll() |
Object |
wait() |
Object |
|
wait(long) |
Object |
wait(long, int) |
Object |
|
 |
|
| Void |  |
Byte |
