Java.lang.Boolean Java中的类

Java在Java.lang 包中提供了一个包装类Boolean 。 Boolean 类将原始类型 boolean 的值包装在一个对象中。 Boolean 类型的对象包含一个字段，其类型为布尔值。

此外，该类提供了有用的方法，例如将布尔值转换为字符串和将字符串转换为布尔值，同时处理布尔变量。

创建一个布尔对象

Boolean 类提供了两个构造函数来创建 Boolean 对象。

下面的语句创建一个包含 value 参数的布尔对象。
```
Boolean b = new Boolean(boolean value);
```
下面的语句创建一个布尔对象，如果字符串参数不为空并且等于字符串“true”，则该对象包含值 true，忽略大小写，否则创建值为 false 的布尔对象。
```
Boolean b = new Boolean(String s);
```

领域：

static Boolean FALSE :对应于原始值 false 的布尔对象。
static Boolean TRUE ：对应于原始值 true 的布尔对象。
static Class ：表示基本类型 boolean 的 Class 对象。

方法：

static boolean parseBoolean(String s) ：此方法将字符串参数解析为布尔值。如果字符串参数不为空，则返回的布尔值表示值 true，并且忽略大小写，等于字符串“true”，否则返回 false。

Syntax : 
public static boolean parseBoolean(String s)
Parameters : 
s - the String containing the boolean representation to be parsed
Returns :
the boolean represented by the string argument

// Java program to demonstrate parseBoolean() method
public class Test
{
    public static void main(String[] args)
    {
        // parsing different Strings
        boolean b1 = Boolean.parseBoolean("True");
        boolean b2 = Boolean.parseBoolean("TruE");
        boolean b3 = Boolean.parseBoolean("False");
        boolean b4 = Boolean.parseBoolean("FALSE");
        boolean b5 = Boolean.parseBoolean("GeeksForGeeks");
          
        System.out.println(b1);
        System.out.println(b2);
        System.out.println(b3);
        System.out.println(b4);
        System.out.println(b5);
          
    }
}

输出：

true
true
false
false
false

boolean booleanValue() ：此方法将此布尔对象的值作为布尔原语返回。

Syntax : 
public boolean booleanValue()
Parameters : 
NA
Returns :
the primitive boolean value of this object.

// Java program to demonstrate booleanValue() method
public class Test
{
    public static void main(String[] args)
    {
        // creating different Boolean objects
        Boolean b1 = new Boolean("True");
        Boolean b2 = new Boolean("False");
        Boolean b3 = new Boolean("GeeksForGeeks");
          
        // getting primitive boolean value
        boolean b4 = b1.booleanValue();
        boolean b5 = b2.booleanValue();
        boolean b6 = b3.booleanValue();
          
        System.out.println(b4);
        System.out.println(b5);
        System.out.println(b6);
          
    }
}

输出：

true
false
false

static Boolean valueOf(boolean b) ：此方法返回一个表示指定布尔值的布尔实例。如果指定的布尔值为 true，则返回 Boolean.TRUE；如果为 false，则此方法返回 Boolean.FALSE。接下来讨论该方法的另一个变体。

Syntax : 
public static boolean valueOf(boolean b)
Parameters : 
b - a boolean value.
Returns :
a Boolean object representing b.

// Java program to demonstrate valueOf() method
public class Test
{
    public static void main(String[] args)
    {
        // creating boolean variable
        boolean b1 = true;
        boolean b2 = false;
          
        // getting Boolean objects from boolean variables
        Boolean b3 = Boolean.valueOf(b1);
        Boolean b4 = Boolean.valueOf(b2);
          
        System.out.println(b3);
        System.out.println(b4);
          
    }
}

输出：

true
false

static Boolean valueOf(String s) ：此方法返回一个布尔值，其值由指定的字符串's' 表示。返回的布尔值表示如果字符串参数不为空并且等于字符串“true”，忽略大小写，则返回一个真值。

Syntax : 
public static boolean valueOf(String s)
Parameters : 
s - a string
Returns :
a Boolean value represented by the string

// Java program to demonstrate valueOf() method
public class Test
{
    public static void main(String[] args)
    {
        // creating boolean variable using different Strings
        Boolean b1 = Boolean.valueOf("true");
        Boolean b2 = Boolean.valueOf("TRue");
        Boolean b3 = Boolean.valueOf("False");
        Boolean b4 = Boolean.valueOf("GeeksForGeeks");
        Boolean b5 = Boolean.valueOf(null);
          
        System.out.println(b1);
        System.out.println(b2);
        System.out.println(b3);
        System.out.println(b4);
        System.out.println(b5);
          
    }
}

输出：

true
true
false
false
false

static String toString(boolean b) ：此方法返回一个表示指定布尔值的 String 对象。如果指定的布尔值为真，则返回字符串“true”，否则返回字符串“false”。接下来讨论此方法的其他变体。

Syntax : 
public static String toString(boolean b)
Parameters : 
b - the boolean to be converted
Returns :
the string representation of the specified boolean

// Java program to demonstrate toString() method
public class Test
{
    public static void main(String[] args)
    {
        // creating boolean variable
        boolean b1 = true;
        boolean b2 = false;
          
        // getting String value of the primitives boolean
        String str1 = Boolean.toString(b1);
        String str2 = Boolean.toString(b2);
          
        System.out.println(str1);
        System.out.println(str2);
    }
}

输出：

true
false

String toString() ：此方法返回一个表示此布尔值的 String 对象。如果此对象表示值 true，则返回等于“true”的字符串。否则，返回字符串“false”。

Syntax : 
public String toString()
Parameters : 
NA
Returns :
a string representation of this object
Overrides :
toString in class Object

// Java program to demonstrate toString() method
public class Test
{
    public static void main(String[] args)
    {
        // creating different Boolean objects
        Boolean b1 = new Boolean("True");
        Boolean b2 = new Boolean("False");
        Boolean b3 = new Boolean("GeeksForGeeks");
        Boolean b4 = new Boolean(null);
      
          
        // getting String value of Boolean objects
        String str1 = b1.toString();
        String str2 = b2.toString();
        String str3 = b3.toString();
        String str4 = b4.toString();
          
        System.out.println(str1);
        System.out.println(str2);
        System.out.println(str3);
        System.out.println(str4);
    }
}

输出：

true
false
false
false

int hashCode() ：此方法返回此布尔对象的哈希码。请注意，true 的哈希码是 1231，false 的哈希码是 1237。要找到选择此整数作为哈希码的原因，请参阅此处。

Syntax : 
public int hashCode()
Parameters : 
NA
Returns :
the integer 1231 if this object represents true;
returns the integer 1237 if this object represents false
Overrides :
hashCode in class Object

// Java program to demonstrate hashCode() method
public class Test
{
    public static void main(String[] args)
    {
        // creating different Boolean objects
        Boolean b1 = new Boolean("True");
        Boolean b2 = new Boolean("False");
        Boolean b3 = new Boolean("TRue");
        Boolean b4 = new Boolean(null);
      
        System.out.println(b1.hashCode());
        System.out.println(b2.hashCode());
        System.out.println(b3.hashCode());
        System.out.println(b4.hashCode());
    }
}

输出：

boolean equals(Object obj) ：如果参数不为 null 并且是表示与此对象相同的布尔值的布尔对象，则此方法返回 true。

Syntax : 
public boolean equals(Object obj)
Parameters : 
obj - the object to compare with.
Returns :
true if the Boolean objects represent the same value; 
false otherwise
Overrides :
equals in class Object

// Java program to demonstrate equals() method
public class Test
{
    public static void main(String[] args)
    {
        // creating different Boolean objects
        Boolean b1 = new Boolean("True");
        Boolean b2 = new Boolean("False");
        Boolean b3 = new Boolean("TrUe");
        Boolean b4 = new Boolean(null);
          
      
        // checking equality of Boolean objects
        System.out.println(b1.equals(b2));
        System.out.println(b2.equals(b4));
        System.out.println(b1.equals(b3));
        System.out.println(b1.equals(b4));
    }
}

输出：

false
true
true
false

int compareTo(Boolean b) ：此方法将这个布尔实例与传递的参数“b”“比较”。

Syntax : 
public int compareTo(Boolean b)
Parameters : 
b - the Boolean instance to be compared
Returns :
zero if this object represents the same boolean value as the argument; 
a positive value if this object represents true and the argument represents false;
a negative value if this object represents false and the argument represents true.
Throws :
NullPointerException - if the argument is null

// Java program to demonstrate compareTo() method
public class Test
{
    public static void main(String[] args)
    {
        // creating different Boolean objects
        Boolean b1 = new Boolean("True");
        Boolean b2 = new Boolean("False");
        Boolean b3 = new Boolean("TRue");
        Boolean b4 = new Boolean(null);
      
        //comparing b1,b2,b3,b4
        System.out.println(b1.compareTo(b2));
        System.out.println(b1.compareTo(b3));
        System.out.println(b2.compareTo(b1));
        System.out.println(b1.compareTo(b4));
        System.out.println(b2.compareTo(b4));
          
        // The following statement throws NullPointerExcetion
        //  System.out.println(b1.compareTo(null));
    }
}

输出：

int compare(boolean x, boolean y) ：此方法用于“比较”原始布尔变量。

Syntax : 
public static int compare(boolean x, boolean y)
Parameters : 
x - the first boolean to compare
y - the second boolean to compare
Returns :
zero if x is same boolean value as y; 
a positive value x is true and y is false;
a negative value if x is false and y is true;
Throws :
NullPointerException - if the argument is null

// Java program to demonstrate compare() method
public class Test
{
    public static void main(String[] args)
    {
        // creating boolean variable
        boolean b1 = true;
        boolean b2 = false;
        boolean b3 = true;
        boolean b4 = false;
          
        //comparing b1,b2,b3,b4
        System.out.println(Boolean.compare(b1, b2));
        System.out.println(Boolean.compare(b1, b3));
        System.out.println(Boolean.compare(b2, b1));
        System.out.println(Boolean.compare(b2, b4));
          
        // The following statement throws NullPointerExcetion
        //  System.out.println(Boolean.compare(b1, null));
    }
}

输出：