===== CS302 TOOL BOX =====
T > COIN TOSS SIMULATOR
G > GRADE ESTIMATOR
C > COLOR CHALLENGE
Q > QUIT
Type code letter for your choices: h
Invalid selection. Please try agian:
t
Invalid selection. Please try agian:
T
^这是我运行程序并给出错误猜测时得到的结果。该循环是为了验证用户输入而进行的，因此它完全失败了。关于我做错了什么有什么想法吗？感谢您的宝贵时间!
}
System.out.println("===== CS302 TOOL BOX =====");
System.out.println("T > COIN TOSS SIMULATOR");
System.out.println("G > GRADE ESTIMATOR");
System.out.println("C > COLOR CHALLENGE");
System.out.println("Q > QUIT");
System.out.print("Type code letter for your choices: ");
boolean code_letter;
String code_choice = scanner.next();
do {
if (code_choice.toUpperCase().equals("Q")
|| (code_choice.toUpperCase()).equals("C")
|| (code_choice.toUpperCase()).equals("G")
|| (code_choice.toUpperCase()).equals("T")) {
code_letter = true;
}
else {
System.out.println("Invalid selection. Please try agian: ");
code_letter = false;
scanner.next();
}
} while (!(code_letter));
{
System.out.println("you did it?");
}
}
}
最佳答案
在 do-while 循环中初始化 code_choice 变量，否则在条件测试之前，该变量将不会在循环的每次迭代中重新初始化.
String code_choice = scanner.next();
像这样
//declared it outside to take care of the scope
String code_choice = null;
do {
//initialize it every time before you perform the conditional test.
//This increases the readability!
code_choice = scanner.next();
if (code_choice.toUpperCase().equals("Q")
|| (code_choice.toUpperCase()).equals("C")
|| (code_choice.toUpperCase()).equals("G")
|| (code_choice.toUpperCase()).equals("T")) {
code_letter = true;
}
else {
System.out.println("Invalid selection. Please try agian: ");
code_letter = false;
}
} while (!(code_letter));
希望这有帮助!
关于java - 输入验证(do-while 循环)出现故障，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/21844025/