String.equals 与 == [英] String.equals versus ==

问题描述

这段代码将一个字符串分割成tokens并存储在一个字符串数组中，然后将一个变量与第一个home进行比较......为什么它不起作用?

This code separates a string into tokens and stores them in an array of strings, and then compares a variable with the first home ... why isn't it working?

public static void main(String...aArguments) throws IOException {

    String usuario = "Jorman";
    String password = "14988611";

    String strDatos = "Jorman 14988611";
    StringTokenizer tokens = new StringTokenizer(strDatos, " ");
    int nDatos = tokens.countTokens();
    String[] datos = new String[nDatos];
    int i = 0;

    while (tokens.hasMoreTokens()) {
        String str = tokens.nextToken();
        datos[i] = str;
        i++;
    }

    //System.out.println (usuario);

    if ((datos[0] == usuario)) {
        System.out.println("WORKING");
    }
}

推荐答案

使用 string.equals(Object other) 比较字符串的函数，而不是 == 运算符.

该函数检查字符串的实际内容，== 运算符检查对对象的引用是否相等.请注意，字符串常量通常是内嵌的"，因此实际上可以将具有相同值的两个常量与 == 进行比较，但最好不要依赖它.

The function checks the actual contents of the string, the == operator checks whether the references to the objects are equal. Note that string constants are usually "interned" such that two constants with the same value can actually be compared with ==, but it's better not to rely on that.

if (usuario.equals(datos[0])) {
    ...
}

注意:比较是在 'usuario' 上完成的，因为这保证在您的代码中非空，尽管您仍然应该检查 datos 数组中是否确实有一些标记，否则您'会得到一个数组越界异常.

NB: the compare is done on 'usuario' because that's guaranteed non-null in your code, although you should still check that you've actually got some tokens in the datos array otherwise you'll get an array-out-of-bounds exception.

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