10，equals和 ==的区别

String a1 = "123";
        String a2 = "123";
        
        System.out.println(a1==a2);//true
        
        
        EqualsTest e1 = new EqualsTest();
        EqualsTest e2 = new EqualsTest();
        
        System.out.println(e1==e2);//false

区别：地址不相等