打印字符串比较结果时得到奇怪的输出 [英] Getting strange output when printing result of a string comparison

问题描述

我遇到了这一行的问题（如下所示）：

I am facing a problem with this line (commented below):

System.out.println("Using == ::"+s3==s4)

输出 false 。

然而， System.out.println（s3 == s4）输出 true 。

现在，我无法理解为什么会得到这个结果：

Now, I am not able to understand why I am getting this result:

public class string {
    public static void main(String[] args){
        String s3="Shantanu";
        String s4=s3;
        String s1=new String("java");
        String s2=new String("javaDeveloper");

        System.out.println("Using Equals Method::"+s1.equals(s2));
        System.out.println("Using Equals Method::"+s3.equals(s4));
        System.out.println("Using == ::"+s3==s4);//Problem is here in this line
        System.out.println(s1+"Directly printing the s2 value which is autocasted from superclass to string subclass ");
        System.out.println("Directly printing the s1 value which is autocasted from superclass to string subclass "+s2);
        System.out.println(s3);
    }
}

Output-Using Equals Method::false
Using Equals Method::true
Using == ::false
java Directly printing the s2 value which is autocasted from superclass to string subclass
Directly printing the s1 value which is autocasted from superclass to string subclass javaDeveloper

推荐答案

你缺少一组括号：

System.out.println("Using == ::" + (s3==s4));

在您的版本中，使用== ::+ s3 正在通过 == 与 s4 进行比较，这不是你想要的。

In your version, "Using == ::" + s3 is being compared via == to s4, which isn't what you want.

通常， + 有更高的 precedence 比 == ，这就是为什么使用== ::+ s3 == s4 正在评估为（使用== ::+ s3）== s4 。

In general, + has a higher precedence than ==, which is why "Using == ::" + s3==s4 is being evaluated as ("Using == ::" + s3) == s4.

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