字符串习题

1.习题1

输出下列代码结果并说明原因
案例1：
public static void main(String[] args) {

    String a = "a1";

    String b = "a" + 1;

    System.out.println(a == b);

true
}
案例2：
public static void main(String[] args) {

    String a = "ab";

    String bb = "b";

    String b = "a" + bb;

    System.out.println(a == b);

false
}
案例3：（选做题）
public static void main(String[] args) {

    String a = "ab";

    final String bb = "b";

        String b = "a" + bb;
    
       System.out.println(a == b);

true
}