Question

这是一个非常简单的代码：

  public class Test2 {

public static void main(String[] args)  {
        String a = "hello2"; 
        final String b = "hello";
        String d = "hello";
        String c = b + 2; 
        String e = d + 2;
        System.out.println((a));
        System.out.println((c));
        System.out.println((e));
        System.out.println((a == c));
        System.out.println((a == e));

    }
}

输出是：

hello2
hello2
hello2
true
false

请告诉我为什么最后一个是＆＃39; false＆＃39;谢谢

Answer 1

public static void main(String[] args)  {
        String a = "hello2"; 
        final String b = "hello"; // this will be a compile-time constant. `final String` makes a string compile-time-constant.
        String d = "hello";
        String c = b + 2; // The compiler will replace b+2 by "hello2"
        String e = d + 2; // d is not final. Hence value of b will be calculated at runtime.
        System.out.println((a));
        System.out.println((c));
        System.out.println((e));
        System.out.println((a == c));
        System.out.println((a == e));

    }

Answer 2

这是因为您要比较对象，而不是实际的String值。使用.equals()比较字符串值。

Answer 3

您应该将字符串值与equals()而不是==运算符进行比较。 ==比较引用而不是值。

需要有关此Java输出的帮助

3 个答案: