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Java ==

admin 11月 12, 2020 0

`==`

对于基本数据类型，也称原始数据类型（byte,short,char,int,long,float,double,boolean）== 比较的是他们的值
复合数据类型(类) ==比较的一定是他们是否是同一个Object

特殊情况

对于基本类型，auto boxing会有缓存，缓存范围：true, false, a byte, a char in the range u0000 to u007f, or an int or short number between -128 and 127
对于字符串常量，String类会有缓存

所以

Integer a = 10;
Integer b = 10;
System.out.println(a == b); // => true

Integer c = new Integer(10);
System.out.println(a == c); // => false

Integer d = 128;
Integer e = 128;
System.out.println(d == e); // => false;

String s1 = "abc";
String s2 = "abc";
System.out.println(s1 == s2); // => true

String s3 = new String("abc");
System.out.println(s1 == s3); // => false