Java.lang.Boolean 类方法

布尔类方法。

关于 ：
Java.lang.Boolean 类将原始类型的布尔值包装在一个对象中。
类声明

public final class Boolean
   extends Object
      implements Serializable, Comparable

构造函数：

Boolean(boolean val) : Assigning Boolean object representing the val argument.
Boolean(String str)  : Assigning Boolean object representing the value true or false
                              according to the string.

方法 ：

• booleanValue() : Java.lang.Boolean.booleanValue()用于将布尔对象的值分配给布尔原语。
  句法 ：

public boolean booleanValue()
Returns : 
primitive boolean value of the boolean object.

• compareTo() : Java.lang.Boolean.compareTo(Boolean arg)将此布尔实例与传递的布尔实例进行比较。
  句法 ：

public int compareTo(Boolean arg)
Parameter : 
arg : boolean instance to be compared with this instance.
Returns :
0 : if this instance = argumented instance.
+ve value : if this instance > argumented instance.
-ve value : if this instance < argumented instance.

• hashCode() : Java.lang.Boolean.hashCode()返回分配的布尔对象的哈希码值。
  句法 ：

public int hashCode()
Returns : 
1231 : if the boolean value of object is true.
1237 : if the boolean value of object is false.

• toString() : Java.lang.Boolean.toString()根据其值返回布尔对象的字符串表示形式。
  句法 ：

public String toString()
Returns : 
string value - 'true' if boolean object is true, else false.

执行：

Java

// Java program illustrating Boolean class methods
// booleanValue(), compareTo(), hashCode(), toString()
import java.lang.*;
public class NewClass
{
 
    public static void main(String[] args)
    {
        // Creating a boolean object and assigning value to it.
        Boolean bool1 = new Boolean(true);
        Boolean bool2 = new Boolean(false);
        System.out.println("Boolean object - bool1 : "+bool1);
        System.out.println("Boolean object - bool2 : "+bool2);
 
 
        // Creating a boolean primitive bool2
        boolean bool3, bool4 ;
        // Use of booleanValue()
        // Assigning object value to primitive variable.
        bool3 = bool1.booleanValue();
        System.out.println("Primitive value of object i.e. bool3 : "+bool3);
 
        bool4 = bool2.booleanValue();
        System.out.println("Primitive value of object i.e. bool4 : "+bool4);
        System.out.println("");
 
 
        // Comparing two boolean instances bool1 and bool2
        // Use of compareTo() method
        int comp = bool1.compareTo(bool2);
        if (comp > 0)
            System.out.println("bool1 is greater than bool2 as comp = "+comp);
        if (comp == 0)
            System.out.println("bool1 is equal to bool2 as comp = "+comp);
        if (comp < 0)
            System.out.println("bool1 is less than bool2 as comp = "+comp);
        System.out.println("");
 
        // HashCode value of the boolean object.
        // use of hashCode() method
        int h1 = bool1.hashCode();
        int h2 = bool2.hashCode();
        System.out.println("Hash Code value of bool1 : " + h1);
        System.out.println("Hash Code value of bool2 : " + h2);
        System.out.println("");
 
        // String representation of the boolean object
        // Use of toString() method.
        String s1, s2;
        s1 = bool1.toString();
        s2 = bool2.toString();
        System.out.println("String value of bool1 : " + s1);
        System.out.println("String value of bool2 : " + s2);
    }
}

输出：

Boolean object - bool1 : true
Boolean object - bool2 : false
Primitive value of object i.e. bool3 : true
Primitive value of object i.e. bool4 : false

bool1 is greater than bool2 as comp = 1

Hash Code value of bool1 : 1231
Hash Code value of bool2 : 1237

String value of bool1 : true
String value of bool2 : false

• getBoolean() : Java.lang.Boolean.getBoolean(String arg)返回真，如果“真”值被分配给系统属性。
  要为属性分配任何值，我们使用 System 类的 setProperty() 方法。
  句法 ：

public static boolean getBoolean(String arg)
Parameters : 
arg - name of the property
Returns : 
true : if 'true' value is assigned to the System property.
false : if no such property exists or if exists then no value is assigned to it.

执行：

Java

// Java program illustrating getBoolean() method
import java.lang.*; // Using Boolean and System classes
public class NewClass
{
    public static void main(String[] args)
    {
        /* Use of getBoolean() to check whether
        any value is assigned to Property - p1, p2 or not */
        boolean b1 = Boolean.getBoolean("p1");
        boolean b2 = Boolean.getBoolean("p2");
 
        System.out.println("Bool Value of p1 : "+b1);
        System.out.println("Bool Value of p2 : "+b2);
        System.out.println("");
        System.out.println("Since, no value assigned to p1, p2, Bool value is false");
        System.out.println("Assign value to p1,p2 using java.lang.System.setProperty()");
 
        System.out.println("");
 
        System.setProperty("p1","true");
        System.setProperty("p2","Cool");
 
        boolean b3 = Boolean.getBoolean("p1");
        boolean b4 = Boolean.getBoolean("p2");
 
        System.out.println("Bool Value of p1 : " + b3);
        System.out.println("Bool Value of p2 : " + b4);
    }
}

输出：

Bool Value of p1 : false
Bool Value of p2 : false

Since, no value assigned to p1, p2, Bool value is false
Assign value to p1,p2 using java.lang.System.setProperty()

Bool Value of p1 : true
Bool Value of p2 : false

• 价值（）： Java。 Java.lang.Boolean.valueOf(boolean arg)返回分配给布尔变量的值。
  如果分配了真值，则返回真，否则返回假。
  要为属性分配任何值，我们使用 System 类的 setProperty() 方法。
  句法 ：

public static Boolean valueOf(boolean arg)
Parameters : 
arg - boolean variable
Returns : 
True : if true value is assigned to the boolean variable, else false 

• parseBoolean() : Java.lang.Boolean.parseBoolean(String s)返回字符串参数的真或假值（被它作为布尔值）。
  这是不区分大小写的方法。
  句法 ：

public static boolean parseBoolean(String arg)
Parameters : 
arg - String argument taken as Boolean
Returns : 
Boolean value of a String argument

执行：

Java

// Java program illustrating parseBoolean() and valueOf() method
import java.lang.*;
public class NewClass
{
    public static void main(String[] args)
    {
        boolean b1 = false;
        boolean b2 = true;
         
        // Use of valueOf() method
        boolean val1 = Boolean.valueOf(b1);
        boolean val2 = Boolean.valueOf(b2);
 
        System.out.println("Value of b1 : "+ val1);
        System.out.println("Value of b2 : " +val2);
        System.out.println("");
 
        // Use of parseBoolean() method
        String st1, st2, st3;
        st1 = "True";
        st2 = "yes";
        st3 = "true";  // Case insensitive
 
        boolean p1 = Boolean.parseBoolean(st1);
        boolean p2 = Boolean.parseBoolean(st2);
        boolean p3 = Boolean.parseBoolean(st3);
 
        System.out.println("Value of String st1 as Boolean : "+p1);
        System.out.println("Value of String st2 as Boolean : "+p2);
        System.out.println("Value of String st3 as Boolean : "+p3);
    }
}

输出：

Value of b1 : false
Value of b2 : true

Value of String st1 as Boolean : true
Value of String st2 as Boolean : false
Value of String st3 as Boolean : true