使用案例后如何制作Java主菜单循环

Question

我是 Java 的新手，但熟悉其他一些编程语言后，我知道其中很多的基本布局。我苦苦挣扎的一件事是循环菜单，特别是主菜单。

我不知疲倦地研究了它的方法，但似乎没有一个适用于或适用于我的程序。我假设它是我在更基本的程序中遗漏的一些愚蠢和小的东西。

在下面检查它，感谢您提供任何提示。

     import java.util.Scanner;
public class basicCalc {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        Scanner input = new Scanner(System.in);
        boolean mainLoop = true;

        int choice;
        do{
            System.out.println("Calculator Main Menu\n");
            System.out.print("1.) Addition \n");
            System.out.print("2.) Subtraction.\n");
            System.out.print("3.) Multiplication.\n");
            System.out.print("4.) Division.\n");
            System.out.print("5.) Generate Random Number.\n");
            System.out.print("6.) Exit\n");
            System.out.print("\nEnter Your Menu Choice: ");

            choice = input.nextInt();

        }

        while(choice >7);

        switch(choice){

        case 1:
            //Definitions
            int adNumf, adNuml, sum;
            System.out.print("Please Enter The First Number: ");
            adNumf = input.nextInt();
            System.out.print("\nPlease Enter The Second Number: ");
            adNuml = input.nextInt();
            sum = adNumf + adNuml;
            System.out.print("The Sum Of Those Numbers is: " +sum);
            break;

        case 2:
            int subNum1, subNum2, sum2;
            System.out.println("\nPlease Enter The First Number: ");
            subNum1 = input.nextInt();
            System.out.println("Please Enter The Second Number: ");
            subNum2 = input.nextInt();
            sum2 = subNum1 - subNum2;
            System.out.println("The Subtraction Leaves The Number: " +sum2);
            break;

        case 3:
            int multNum1, multNum2, multTotal;

            // Gather Input
            System.out.println("Please Enter The First Number To Multiply: ");
            multNum1 = input.nextInt();
            System.out.println("Please Enter The Second Number To Multiply: ");
            multNum2 = input.nextInt();

            // This will Multiply the Numbers
            multTotal = multNum1 * multNum2;

            //Display Final
            System.out.println("The Multiplied Numbers Are: " +multTotal);
            break;

        case 4:
            //Definitions
            double divNum1, divNum2, divTotal;
            System.out.println("Enter Your Numerator ");
            divNum1 = input.nextInt();
            System.out.println("Enter Your Denominator ");
            divNum2 = input.nextInt();
            if(divNum2 == 0){
                System.out.println("Zero is Not divisable, please select a new denominator: ");
                divNum2 = input.nextInt();
            }
            divTotal = divNum1 / divNum2;
            System.out.println("Your divisor is: " +divTotal);
            break;

        case 5:
            double limL, limH, rand;
            System.out.println("Enter Your Low Limit: ");
            limL = input.nextInt();
            System.out.println("Enter Your High Limit ");
            limH = input.nextInt();

            //Equation to keep numbers within bounds
            rand = limL + (Math.random() * ((limH - limL) + 1));
            System.out.println("Given Your Limits, the Random Number will be: " +rand);
            break;

        case 6:
            System.out.println("Exiting Program...");
            System.exit(0);
             break;
        }

        // Bad Menu Option Direct
    if (choice > 6 || choice < 1){
        System.out.println("This is not a valid Menu Option! Please Select Another.");
        do{
            choice = input.nextInt();
        }
        while(choice < 7 );
    }
    // End bad menu option

    }

}

原文由 Ace Ebert 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

您可以在 while 循环中给出整个代码（从显示菜单）并将条件设为真，以便在使用案例后它会自动重复（因为您正在使用 6 退出）。如果为 eg:10 提供了任何无效输入，则案例将转到默认部分并执行那里的代码

import java.util.Scanner;
public class basicCalc {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    Scanner input = new Scanner(System.in);
    boolean mainLoop = true;

    int choice;
    while(true){
        System.out.println("Calculator Main Menu\n");
        System.out.print("1.) Addition \n");
        System.out.print("2.) Subtraction.\n");
        System.out.print("3.) Multiplication.\n");
        System.out.print("4.) Division.\n");
        System.out.print("5.) Generate Random Number.\n");
        System.out.print("6.) Exit\n");
        System.out.print("\nEnter Your Menu Choice: ");

        choice = input.nextInt();

    switch(choice){

    case 1:
        //Definitions
        int adNumf, adNuml, sum;
        System.out.print("Please Enter The First Number: ");
        adNumf = input.nextInt();
        System.out.print("\nPlease Enter The Second Number: ");
        adNuml = input.nextInt();
        sum = adNumf + adNuml;
        System.out.print("The Sum Of Those Numbers is: " +sum);
        break;

    case 2:
        int subNum1, subNum2, sum2;
        System.out.println("\nPlease Enter The First Number: ");
        subNum1 = input.nextInt();
        System.out.println("Please Enter The Second Number: ");
        subNum2 = input.nextInt();
        sum2 = subNum1 - subNum2;
        System.out.println("The Subtraction Leaves The Number: " +sum2);
        break;

    case 3:
        int multNum1, multNum2, multTotal;

        // Gather Input
        System.out.println("Please Enter The First Number To Multiply: ");
        multNum1 = input.nextInt();
        System.out.println("Please Enter The Second Number To Multiply: ");
        multNum2 = input.nextInt();

        // This will Multiply the Numbers
        multTotal = multNum1 * multNum2;

        //Display Final
        System.out.println("The Multiplied Numbers Are: " +multTotal);
        break;

    case 4:
        //Definitions
        double divNum1, divNum2, divTotal;
        System.out.println("Enter Your Numerator ");
        divNum1 = input.nextInt();
        System.out.println("Enter Your Denominator ");
        divNum2 = input.nextInt();
        if(divNum2 == 0){
            System.out.println("Zero is Not divisable, please select a new denominator: ");
            divNum2 = input.nextInt();
        }
        divTotal = divNum1 / divNum2;
        System.out.println("Your divisor is: " +divTotal);
        break;

    case 5:
        double limL, limH, rand;
        System.out.println("Enter Your Low Limit: ");
        limL = input.nextInt();
        System.out.println("Enter Your High Limit ");
        limH = input.nextInt();

        //Equation to keep numbers within bounds
        rand = limL + (Math.random() * ((limH - limL) + 1));
        System.out.println("Given Your Limits, the Random Number will be: " +rand);
        break;

    case 6:
        System.out.println("Exiting Program...");
        System.exit(0);
         break;
    default :
             System.out.println("This is not a valid Menu Option! Please Select Another");
             break;

    }

    }

    }

   }

原文由 Anoop LL 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

您对要做什么有一个大致的了解，但是您正在使循环结束条件变得比需要的更复杂。尝试使用“默认”选项来捕获超出范围的任何输入。这样您就可以将结束条件简化为“6”（退出情况）。简单地展示：

 do{
  //Menu options
  System.out.print("6.) Exit\n");
  System.out.print("\nEnter Your Menu Choice: ");

  choice = input.nextInt();

  switch(choice){
        //Your cases from 1 to 6.
        default:
            System.out.println("Invalid menu choice; try again.");
            break;
   }
}while(choice != 6);

如果选择选项不适用于您的代码中创建的任何案例，则将调用默认值之后的任何内容。

原文由 Jimmy M. 发布，翻译遵循 CC BY-SA 3.0 许可协议