JAVA中“==”与“equals()”的区别
1、
“= =”比较的是两端是否为同一个对象(或者说是否指向同一个地址),也就是说,比较的是地址,并且要求两端的类型必须相同,可以是父类和子类的继承关系;
2、
equals()是个方法,可以用于String和Object类的比较,当比较String类和基类包装类时,比较的是内容,Object类比较时,比的是否为同一个类。另外equals()不可以用于基类的比较,但可以用于基类的包装类的比较。
3、
典例:
//Object类
JButton bt1 = new JButton();
JButton bt2 = new JButton();
JButton bt3,bt4;
System.out.println(bt1 == bt2);//false
System.out.println(bt1.equals(bt2));//false
//System.out.println(bt3 == bt4);//报错
//System.out.println(bt3.equals(bt4));//报错
//String类
String s1 = new String("abc");
String s2 = new String("abc");
String s3 = "abc", s4 ="abc" ;
System.out.println(s1 == s2);//false
System.out.println(s3 == s4);//true
System.out.println(s1 == s3);//false
System.out.println(s1.equals(s2));//true
System.out.println(s3.equals(s4));//true
System.out.println(s1.equals(s3));//true
//基类
int a = 3;
int b = 4;
int c = 3;
System.out.println(a == b);//false
System.out.println(a == c);//true
//System.out.println(a.equals(c));//报错
//基类包装类
Integer n1 = new Integer(30);
Integer n2 = new Integer(30);
Integer n3 = new Integer(31);
System.out.println(n1 == n2);//false
System.out.println(n1 == n3);//false
System.out.println(n1.equals(n2));//true
System.out.println(n1.equals(n3));//false