Question

在为我的程序编写代码时，我想在继续编写操作之前测试第一部分。虽然我有用户输入，但我希望在每次操作（add，deltete ..）之后显示选项，直到用户按下exit。如何修改我的代码呢？

import java.io.*;
import java.util.*;

public class Records {

    public static void main(String[] args) {
        int choice;
        do {
            System.out.println("1.Add \n 2.Delete \n 3.Update \n 4.Show \n Exit");
            //BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
            //int choice;
            System.out.println("Enter your Choice : ");
            Scanner sc = new Scanner(System.in);
            choice = sc.nextInt();

            switch (choice) {
                case 1: 
                    System.out.println("Getting ready to Add a Record ");
                    //set();
                    break;

                case 2: 
                    System.out.println("Getting ready to Delete a Record ");
                    //delete();
                    break;

                case 3: 
                    System.out.println("Getting ready to Update a Record ");
                    //update();
                    break;

                case 4: 
                    System.out.println("Here is your record ");
                    //display();
                    break;

                case 5: 
                    System.out.println("Out we go.");
                    System.exit(0);
                    //exit();
                    break;

                default: 
                    System.out.println("Try again");
                    break;
            }
        } while ( choice > 5 || choice < 1 );
    }
}

Answer 1

只需将您的while条件更改为：

} while ( choice > 0 && choice < 5 );

Answer 2

虽然我有用户输入，但我希望显示选项每次操作（添加，删除..）完成后直到用户按下退出。

您可以设置int flag=0;，当用户选择退出选项设置标记为1时，告诉循环退出。截至目前，您已经突破> 5或< 1 { {1}}因此无需在default case中添加该条件。

while

严肃编辑

作为Java程序员，我可能建议您使用int flag=0;//Declare outside the loop do{ ... case 5: System.out.println("Out we go."); flag=1;//Set flag to 1 if user enters 5 break; ... } while ( flag!=1 );//Exit the loop when flag==1 //Or directly while ( choice!=5 );基元类型进行标记。

boolean

还有一件事：

使用boolean flag=true;//Declare outside the loop do{ ... case 5: System.out.println("Out we go."); flag=false;//Set flag to 1 if user enters 5 break; ... } while (flag);//Exit the loop when flag==false环绕代码以省略无效输入并再次提示输入。大多数情况下，不建议您吞下try-catch。

Exception

Answer 3

首先确保您的扫描仪确实有一个int，使用sc.hasNextInt()来验证用户输入的数字。要结束“5.Exit”处的do / while循环，只需使用do{...}while(choice!=5)即可。以下代码未经过测试。

import java.io.*;
import java.util.*;

public class Records {

    public static void main(String[] args) {
        int choice;
        do {
            System.out.println("1.Add \n 2.Delete \n 3.Update \n 4.Show \n 5.Exit");
            System.out.println("Enter your Choice : ");
            choice = -1;
            Scanner sc = new Scanner(System.in);

            // validate the next thing in your scanner is an int
            // otherwise, sc.nextInt() might cause an exception
            if (sc.hasNextInt()){
                choice = sc.nextInt();
                switch (choice) {
                    case 1: System.out.println("Getting ready to Add a Record ");
                    // ...
                    break;

                    case 2: System.out.println("Getting ready to Delete a Record ");
                    // ...
                    break;

                    case 3: System.out.println("Getting ready to Update a Record ");
                    // ...
                    break;

                    case 4: System.out.println("Here is your record ");
                    // ...
                    break;

                    case 5: System.out.println("Out we go.");
                    // skip System.exit(0), your main method ends 
                    // automatically when you leave your do/while loop
                    break;

                    default: System.out.println("Try again");
                    break;
                } 
            }
        // if choice == 5 it ends, otherwise, starts over...
        } while ( choice != 5 );
    }

}

Answer 4

只需将你的while循环设为：

} while ( choice!=0 );(The Wrong one)

校正：

} while(choice!=0 && choice<=5)

如何使该程序返回提示，直到用户退出

4 个答案: