关于java String字符串及final的问题

Question

今天测试String字符串时遇到的问题，求大神解决

public void demo1() {
        String a = "abc";
        String ab = "ab";
        String c = "c";
        String abc = ab+c;
        System.out.println(a==abc);//false
    }

private void demo2() {
    final String ab = "ab";
    final String c = "c";
    final String abc = "abc";
    System.out.println(ab+c==abc);//true
}

private void demo3() {
    final String ab ;
    ab ="ab";//这跟demo2()方法差别就是后赋值
    final String c = "c";
    final String abc = "abc";
    System.out.println(ab+c==abc);//false
}

可以解释下吗，三个都不太了解

Answer 1

http://www.kokojia.com/article/14774.html