两个字符串实例看起来相同，但是它们的哈希码不同

Question

    String a = "success";
    String b = "success";

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

    if(a.equals(b)){
        System.out.println("123");
    }

I can't understand why the two string have different hashcode.

    String a = "success";
    String b = "success";

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

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

output:

-1867169789
1954952228
33263331
6413875

Answer 1

You've inserted the zero width no-break space (U+FEFF) character at the beginning of your second string.

That string is actually equal to the following string (no hidden unicode characters): "\success"

That means a and b are not equal and do not have the same hash code.

Answer 2

public class Compare {


    public static void main(String args[])  {

        String a = "success";
        String b = "success";

        char[] aChar = a.toCharArray();
        char[] bChar = b.toCharArray();

        for(int i = 0; i < aChar.length; i++)
        {
            System.out.println((int)aChar[i]);
        }
        System.out.println("");
        for(int i = 0; i < bChar.length; i++)
        {
            System.out.println((int)bChar[i]);
        }
    }

}

The first char of the second string is char 65279. Did you copy the strings from somewhere?

The Strings look the same, but are not. Try typing the "success" text again, then it should work.

Answer 3

当我将代码复制并粘贴到IDE中时，它表明b =的开头双引号“成功实际上是一个奇怪的双引号，而不是标准的双引号。Bizzarrely，我得到了与您相同的结果-代码编译并运行，但输出不同的哈希码。通过将双引号固定为普通的双引号，哈希码现在相同。