java - toString.equals 不起作用？

Question

我试图与工作进行比较，但我一生都无法弄清楚出了什么问题。

StringL l = new StringL();
    l.insert("banana", 0);
    l.insert("orange", 1);
    l.insert("apple",  2);
    l.insert("pear", 3);
    if (!(l.toString().equals("banana, orange, apple, pear")));{
        System.out.println("Test failed: should have returned banana, orange, apple, pear but returned " + l.toString());}
}

但是，当我运行它时，我得到:

Test failed: should have returned banana, orange, apple, pear but returned banana, orange, apple, pear

字符串:

public String toString() {

        String result = ("") ;
        if(size() > 0) 
            result += stringList.get(0);

        for(int i = 1; i < size(); i++) 
            result += ", " + stringList.get(i);

        return result;
    }

Answer 1

你有一个额外的;，你不应该这样做

if (!(l.toString().equals("banana, orange, apple, pear")));{
                                                          ^

这最终看起来像

if (!(l.toString().equals("banana, orange, apple, pear")))
    ;
{
    System.out.println("Test failed: should have returned banana, orange, apple, pear but returned " + l.toString());
}

因此，如果条件为 true，if 就会执行空语句 ;。无论如何，{} block 都会执行。