Question

所以我正在编写这个代码，这是一个关于加法和减法练习的数学程序。我的代码目前是（未完成但编译）：

import java.util.Scanner;
import java.util.Arrays;

public class ElementaryMath{

public static void main(String[] args){


    Scanner in = new Scanner(System.in);

    int t = 1;

    do{
        try{

            System.out.println("-------Elementary Math Practice-------");
            System.out.println( 
                "Please select a mode: \n" +
                "1) Addition \n" +
                "2) Subtraction "
                              );    
            int selection = in.nextInt();

            if(selection == 1){
                Addition();
                }
            else if(selection == 2){
                Subtraction();
                }
            else{
                selection = selection/0 ; 
                }
            t=2;
            }               
            catch(Exception e){
                System.out.println("Invalid input.");
                }
        }
 while(t==1);



}
public static void Addition(){
        Scanner in = new Scanner(System.in);

        int j = 1;

    do{
        try{

            System.out.println("-------Addition Problem Sets-------");
            System.out.println( 
                "Please select a difficulty: \n" +
                "1) Easy \n" +
                "2) Medium \n" +
                "3) Hard \n "
                              );    
            int selection2 = in.nextInt();

            if(selection2 == 1){
                EasyAddition();
                }
            else if(selection2 == 2){
                MediumAddition();
                }
            else if(selection2 == 3){
                HardAddition();
            }
            else{
                selection2 = selection2/0 ; 
                }
            j=2;
            }               
            catch(Exception e){
                System.out.println("Invalid input.");
                }
        }
 while(j==1);

}
public static void Subtraction(){
        Scanner in = new Scanner(System.in);

        int k = 1;

    do{
        try{

            System.out.println("-------Subtraction Problem Sets-------");
            System.out.println( 
                "Please select a difficulty: \n" +
                "1) Easy \n" +
                "2) Medium\n" +
                "3) Hard \n"
                              );    
            int selection3 = in.nextInt();

            if(selection3 == 1){
                EasySubtraction();
                }
            else if(selection3 == 2){
                MediumSubtraction();
                }
            else if(selection3 == 3){
                HardSubtraction();
            }
            else{
                selection3 = selection3/0 ; 
                }
            k=2;
            }               
            catch(Exception e){
                System.out.println("Invalid input.");
                }
        }
 while(k==1);


}

public static void EasyAddition(){

    Scanner in = new Scanner(System.in);
    System.out.print("Enter the amount of problems you wish to do: ");
    int amountEA = in.nextInt();
    int correct = 0;
    EasyAdder(amountEA, correct);
    System.out.println(correct);
    int incorrect = amountEA - correct;
    System.out.println("You have gotten: " +correct+ " correct!");
    System.out.println("You have gotten: " +incorrect+ " incorrect.");
    }





public static void MediumAddition(){System.out.println("Test2");}
public static void HardAddition(){System.out.println("Test3");}
public static void EasySubtraction(){System.out.println("Test4");}
public static void MediumSubtraction(){System.out.println("Test5");}
public static void HardSubtraction(){System.out.println("Test6");}

public static int EasyAdder(int amountEA, int correct){
        Scanner in = new Scanner(System.in);
        int[]answersEasyAdder = new int[amountEA];
        int[]usersanswersEasyAdder = new int[amountEA];

        for(int z=0; z<amountEA ; z++){

            int a = (int)(Math.random()*9+1);
            int b = (int)(Math.random()*9+1);
            int c  = a+b;  
            answersEasyAdder[z] = c;
            System.out.println(Arrays.toString(answersEasyAdder));
            System.out.print("What is: " +a+ " + " +b+ " ?");
            int d = in.nextInt();
            usersanswersEasyAdder[z]=d;
            System.out.println(Arrays.toString(usersanswersEasyAdder));
        }

        for(int l=0; l<amountEA; l++){
            if(answersEasyAdder[l]==usersanswersEasyAdder[l]){
                correct++;
                System.out.println(correct);
            }

        }
        System.out.println(correct);
        return correct;
}


 }

所以我的问题在于EasyAddition和EasyAdder方法。我将正确的密码传递给EasyAdder，以更新用户正确的问题。我试图返回它，但是（这也是为什么System.out.print无处不在，我试图跟踪变量的进度）变量正确似乎在我返回值后没有得到更新。我的回归没有采用正确的方法吗？我有点失落。

Answer 1

您没有将返回值分配给预期变量，这是校正

public static void EasyAddition(){

    Scanner in = new Scanner(System.in);
    System.out.print("Enter the amount of problems you wish to do: ");
    int amountEA = in.nextInt();
    int correct = EasyAdder(amountEA, correct);
    System.out.println(correct);
    int incorrect = amountEA - correct;
    System.out.println("You have gotten: " +correct+ " correct!");
    System.out.println("You have gotten: " +incorrect+ " incorrect.");
    }

Answer 2

方法 easyAdder 正在返回一个迷路的值

这样做：

correct = EasyAdder(amountEA, correct);

这种情况正在发生，因为java正在改变方法内部的int更正值，但这些更改不会影响外部的原语

Java - 变量不会更新

2 个答案: