布尔类将原始类型布尔的值包装在一个对象中。一个布尔类型的对象包含一个类型为布尔的单一字段。
此外,这个类还提供了许多将布尔值转换为String的方法,以及处理布尔值时有用的其他常量和方法。
Boolean boolean1 = new Boolean(true);
Boolean boolean2 = new Boolean("boolean");
类图显示了布尔类所提供的API/方法的列表。
在这篇文章中,我们将学习Booleanwrapper类的几个重要方法。
将字符串参数解析为一个布尔值。如果字符串参数不是空的,并且无视情况,等于字符串 "true",则返回的布尔值代表true。
例子:
private static void parseBoolean(){
// 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);
}
将此布尔对象的值作为一个布尔基元返回。
例子:
private static void booleanValue(){
// 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);
}
返回一个代表指定布尔值的Booleaninstance。如果指定的布尔值为真,该方法返回Boolean.TRUE;如果为假,该方法返回Boolean.FALSE。
例子:
private static void valueOf(){
// 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);
}
返回一个布尔值,其值由指定的字符串表示。如果字符串参数不是空的,并且无视情况,等于字符串 "true",则返回的布尔值代表一个真值。
例子:
private static void valueOf1(){
// 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);
}
返回一个代表指定布尔值的字符串对象。
例子:
private static void toStringTest(){
// 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);
}
返回一个代表此布尔值的字符串对象。
例子:
private static void toStringTest1(){
// 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);
}
返回这个布尔对象的哈希代码。
例子:
private static void hashCodeTest(){
// 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());
}
当且仅当参数不为空,并且是一个与此对象代表相同布尔值的布尔对象时返回真。
例子:
private static void equalsTest(){
// 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));
}
将这个布尔实例与另一个布尔实例进行比较。
例子:
private static void comparetoTest(){
// 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));
}
比较两个布尔值。返回的值与Boolean.valueOf(x).compareTo(Boolean.valueOf(y))所返回的值相同。
例子:
private static void compareTest(){
// 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));
}
###参考
https://docs.oracle.com/javase/8/docs/api/java/lang/Boolean.html
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