java - switch case 中的断言消息不显示

Question

不显示 switch case 中的断言消息。
每当用户输入 < 0 或 > 6 时，它应该输出给定的错误消息。我的断言位于默认部分，并且该消息不会显示。我的代码有什么问题吗？

import java.util.*;
public class DeckOfCards extends Inputs{
//objects
//sets
//int

public DeckOfCards(){
    //some initialization
}

public void setValtyp(String val){
    this.valtyp = valtyp;
}

public String getValtyp(){
    return this.valtyp;
}

public static void main(String args[]){
    int exit = 0;
    do{
        try{
            Scanner input = new Scanner(System.in);
            int option;
            int option2;
            String yesno;
            int back = 0;
            String val;
            String typ;
            System.out.println("Deck of Cards");
            System.out.println("[1]Add");
            System.out.println("[2]Delete");
            System.out.println("[3]Display");
            System.out.println("[4]Search");
            System.out.println("[5]Count");
            System.out.println("[6]Exit");
            System.out.print("Option: ");
            option = input.nextInt();

            switch(option){
                case 1:
                   //codes
                   break;
                case 2:
                    //codes
                    break;
                case 3:
                    //codes
                    break;
                case 4:
                   //codes
                   break;
                case 5:
                    do{
                        try{
                            System.out.println("\nDeck of Cards");
                            System.out.println("[1]Heart");
                            System.out.println("[2]Diamond");
                            System.out.println("[3]Spade");
                            System.out.println("[4]Clover");
                            System.out.println("[5]All");
                            System.out.println("[6]Back");
                            System.out.print("Option: ");
                            option2 = input.nextInt();

                            switch(option2){
                                case 1: 
                                    System.out.println("\nHearts: "+kerds.heart.size());
                                    break;
                                case 2:
                                    System.out.println("\nDiamond: "+kerds.diamond.size());
                                    break;
                                case 3:
                                    System.out.println("\nSpade: "+kerds.spade.size());
                                    break;
                                case 4:
                                    System.out.println("\nClover: "+kerds.clover.size());
                                    break;
                                case 5:
                                    int totalsize;
                                    totalsize = kerds.heart.size() + kerds.diamond.size() + kerds.spade.size() + kerds.clover.size();
                                    System.out.println("\nAll: "+totalsize);
                                    break;
                                case 6:
                                    System.out.println("");
                                    back++;
                                    break;
                                default:
                                    assert false : "Option is out of range. Please try again.\n";
                                    back++;
                                    break;
                            }
                        }
                        catch(InputMismatchException e){
                            System.out.println("Invalid Option! Please try again.\n");
                            back++;
                        }
                    }while(back!=1);
                    break;        
                case 6:
                    exit++;
                    break;
                default:
                    assert false : "Option is out of range. Please try again.\n";
            }
        }
        catch(InputMismatchException e){
            System.out.println("Invalid Option! Please try again.\n");
        }
    }while(exit!=1);
}

}

Answer 1

从中删除back++

      default:
              assert false : "Option is out of range. Please try again.\n";
              back++;
              break;

当用户输入错误的值时，您会跳出循环，因为此时 back == 1 并且您的 do-while 循环结束，并且您的第一个 do-while 循环再次执行，我认为这不是您想要做的，而是在错误的输入下再次运行第二个循环