StringBuilder .equals Java [英] StringBuilder .equals Java

问题描述

class strb
{

    static public void main(String...string)
    {
         StringBuilder s1 = new StringBuilder("Test");
         StringBuilder s2 = new StringBuilder("Test");

         System.out.println(s1);
         System.out.println(s2);
         System.out.println(s1==s2);
         System.out.println(s1.equals(s2)); //Line 1
         System.out.println(s1.toString()==s2.toString()); //Line 2
         if(s1.toString()==s2.toString())System.out.println("True"); //Line 3
    }

}

输出是

And the output is

Test
Test
false
false

在.equals上快速提问。

Just have a quick question on .equals.

无论对象内容如何， .equals 只有当两个对象引用都指向同一个对象时才返回true？

Regardless of the object content, does .equals return true only if both the object references point to the same object ?

编辑：现在我理解关于 .equals 的部分，但为什么第2行和第3行也不会返回 true ？

EDIT : Now I understand the part about the .equals but why does Line 2 and Line 3 also not return true ?

编辑：我相信 == 查看引用变量的地址，因此s1和s2不能相等。如果我的假设不对，请更正我

EDIT : I believe == looks at the reference variable's address and so s1 and s2 cannot be equal.correct me if my assumption is not right

推荐答案

是， StringBuilder不会覆盖Object的.equals（）函数，这意味着两个对象引用不相同，结果为false。

Yes, StringBuilder does not override Object's .equals() function, which means the two object references are not the same and the result is false.

对于 StringBuilder ，你可以使用 s1.toString（）。equals（s2.toString（））

对于编辑，您在两个不同的String对象上调用 == 运算符。 == 运算符将返回false，因为对象不同。要比较字符串，您需要使用 String.equals（）或 String.equalsIgnoreCase（）

For your edit, you're calling the == operator on two different String objects. The == operator will return false because the objects are different. To compare Strings, you need to use String.equals() or String.equalsIgnoreCase()

这与你之前遇到的问题相同

It's the same problem you were having earlier

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