Java：带有 switch 语句的 do-while 循环
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Java: do-while loop with switch statement
提问by ccaulfield
Language: Java
语言：Java
boolean x = false;
String letter = "NULL";
do{
System.out.print("Enter grade (one character): ");
letter = sc.next();
switch (letter) {
case "a":
x=true;
break;
case "A":
x=true;
break;
case "b":
x=true;
break;
case "B":
x=true;
break;
case "c":
x=true;
break;
case "C":
x=true;
break;
case "d":
x=true;
break;
case "D":
x=true;
break;
case "f":
x=true;
break;
case "F":
x=true;
break;
default:
System.out.println("Invalid grade - must enter A,B,C,D,F (upper or lower case)");
System.out.println(x);
break;
}
System.out.println(x);
}
while(x=false);
--------------result output-----------------------------------result output--------------------------
--------------结果输出-------------------- -结果输出--------------------------
Since I am new, I need a 10 reputation to post pictures of the output...so here is the output by typing it out...
因为我是新手，所以我需要 10 个声望来发布输出的图片......所以这是通过输入输出......
//this is for if I enter String "e"
//这是为了如果我输入字符串“e”
Enter grade (one character): e Invalid grade - must enter A,B,C,D,F (upper or lower case)
输入成绩（一个字符）： e 成绩无效 - 必须输入 A、B、C、D、F（大写或小写）
false
错误的
false
错误的
//this is for if I enter String "A"
//这是为了如果我输入字符串“A”
Enter grade (one character): A
输入等级（一个字符）：A
Invalid grade - must enter A,B,C,D,F (upper or lower case)
成绩无效 - 必须输入 A、B、C、D、F（大写或小写）
true
真的
The question***:For my output,when I enter "e", I was hoping to see something like
问题***：对于我的输出，当我输入“e”时，我希望看到类似
Enter grade (one character): e
输入等级（一个字符）：e
Invalid grade - must enter A,B,C,D,F (upper or lower case)
成绩无效 - 必须输入 A、B、C、D、F（大写或小写）
false
错误的
false
错误的
//loops through
//循环
Enter grade (one character):
输入等级（一个字符）：
So I was hoping that when I entered "e" it would make it false...and then start at the beginning until a result finally is entered that is: A,B,C,D,F (upper or lower case)
所以我希望当我输入“e”时它会使它成为假......然后从头开始直到最终输入结果：A，B，C，D，F（大写或小写）
What is my mistake? I have been trying to brainstorm it myself, but I thought I would see what you guys have to say....
我的错误是什么？我一直试图自己集思广益，但我想我会看看你们要说什么......
If you think the strategy I am using to get the output is not the best....What strategy/logic would you recommend?
如果您认为我用来获得输出的策略不是最好的……您会推荐什么策略/逻辑？
Thanks for the help!
谢谢您的帮助！
采纳答案by Jon Kiparsky
while(x=false);
This is wrong. (should be ==)
这是错误的。（应该是==）
回答by CoderCroc
Yes =is assignment operator you have to use ==to check equality and other than that,note here your switch can be reduce to following and currently you have redundant code you can better use if statement with ||operator here.
是的，=您必须使用赋值运算符==来检查相等性，除此之外，请注意，此处您的 switch 可以简化为跟随，目前您有多余的代码，您可以||在这里更好地使用 if 语句与运算符。
switch (letter) {
case "a":
case "A":
case "b":
case "B":
case "c":
case "C":
case "d":
case "D":
case "f":
case "F":
x=true;
break;
default:
//...
回答by Donal
You can simplify the switch statement even further. By converting the letter to upper case you are checking for both upper and lower case. For example:
您可以进一步简化 switch 语句。通过将字母转换为大写，您可以同时检查大写和小写。例如：
do{
System.out.print("Enter grade (one character): ");
letter = sc.next();
switch (letter.toUpperCase()) {
case "A":
case "B":
case "C":
case "D":
case "F":
x=true;
break;
default:
System.out.println("Invalid grade - must enter A,B,C,D,F (upper or lower case)");
break;
}
} while(x==false);
System.out.println(x);
