java - 只要用户输入不等于某些单词就运行的 while 循环不起作用？

Question

我不明白为什么这不起作用。无论我输入什么内容，程序总是会重新提示我，即使它是有效的操作词。

String action = "";
        do {
        System.out.print("Enter what you want to do (ADD, REMOVE, "
                   + "LIST, SAVE, SORT): ");
        action = keyboard.next();
        } while ((!(action.equalsIgnoreCase("ADD")) 
                || !(action.equalsIgnoreCase("REMOVE")) 
                || !(action.equalsIgnoreCase("LIST")) 
                || !(action.equalsIgnoreCase("SAVE")) 
                || !(action.equalsIgnoreCase("SORT"))));

Answer 1

正确。您使用了 or，但您想要 and。

((!(action.equalsIgnoreCase("ADD")) 
            && !(action.equalsIgnoreCase("REMOVE")) 
            && !(action.equalsIgnoreCase("LIST")) 
            && !(action.equalsIgnoreCase("SAVE")) 
            && !(action.equalsIgnoreCase("SORT"))));

每个单词都满足测试，不添加或不删除。您可以申请De Morgan's Laws就像，

(!(action.equalsIgnoreCase("ADD")  
        || action.equalsIgnoreCase("REMOVE") 
        || action.equalsIgnoreCase("LIST") 
        || action.equalsIgnoreCase("SAVE") 
        || action.equalsIgnoreCase("SORT")))