循环用户输入直到满足条件

我需要让用户输入一个数字作为范围的开头，然后输入另一个数字作为范围的结尾。 起始编号必须为0或更大，结束编号不能大于1000.这两个编号必须可以被10整除。我找到了一种方法来满足这些条件，但是如果它们不符合我的程序只是告诉用户他们的输入不正确。 我是否可以对其进行编码，以便在用户输入后检查以确保满足条件，如果它们没有循环返回并再次输入。 这是我到目前为止的代码。

Scanner keyboard = new Scanner(System.in); int startr; int endr; System.out.println("Enter the Starting Number of the Range: "); startr=keyboard.nextInt(); if(startr%10==0&&startr>=0){ System.out.println("Enter the Ending Number of the Range: "); endr=keyboard.nextInt(); if(endr%10==0&&endr<=1000){ }else{ System.out.println("Numbers is not divisible by 10"); } }else{ System.out.println("Numbers is not divisible by 10"); } 

Answer 1

轻松做事：

 Scanner keyboard = new Scanner(System.in); int startr, endr; boolean good = false; do { System.out.println("Enter the Starting Number of the Range: "); startr = keyboard.nextInt(); if(startr % 10 == 0 && startr >= 0) good = true; else System.out.println("Numbers is not divisible by 10"); } while (!good); good = false; do { System.out.println("Enter the Ending Number of the Range: "); endr = keyboard.nextInt(); if(endr % 10 == 0 && endr <= 1000) good = true; else System.out.println("Numbers is not divisible by 10"); } while (!good); // do stuff 

Answer 2

你需要使用一段时间，例如：

 while conditionsMet is false // gather input and verify if user input valid then conditionsMet = true; end loop 

应该这样做。

Answer 3

通用程序是：

1. 以无限循环读取输入。
2. break; 语句在满足条件时退出循环。

例：

 Scanner keyboard = new Scanner(System.in); int startr, endr; for (;;) { System.out.println("Enter the starting number of the range: "); startr = keyboard.nextInt(); if (startr >= 0 && startr % 10 == 0) break; System.out.println("Number must be >= 0 and divisible by 10."); } for (;;) { System.out.println("Enter the ending number of the range: "); endr = keyboard.nextInt(); if (endr <= 1000 && endr % 10 == 0) break; System.out.println("Number must be <= 1000 and divisible by 10."); } 

如果在无效输入后您只想显示错误消息而不重复初始提示消息，请在循环上方/外部移动初始提示消息。

如果您不需要单独的错误消息，则可以重新安排代码以使用do-while循环来检查条件，这只是一点点：

 Scanner keyboard = new Scanner(System.in); int startr, endr; do { System.out.println("Enter the starting number of the range."); System.out.println("Number must be >= 0 and divisible by 10: "); startr = keyboard.nextInt(); } while (!(startr >= 0 && startr % 10 == 0)); do { System.out.println("Enter the ending number of the range."); System.out.println("Number must be <= 1000 and divisible by 10: "); endr = keyboard.nextInt(); } while (!(endr <= 1000 && endr % 10 == 0));