无法弄清楚为什么我的程序不打印数组内容

Question

I'm trying to create the 24 game in java to practice. The 24 Game is an arithmetical game in which the objective is to find a way to manipulate four integers so that the end result is 24. Addition, subtraction, multiplication, or division in any order of the numbers may be used to make the four digits operations from one to nine equal 24.

The rules are simple: you have to use each number only once and only the 4 numbers that were read from the user to find one equation to obtain 24.

My issue is I am not receiving any output after the program completes. The issue could be in the append(String equation) method which is used to prevent duplicate answers and to add the correct equations to the ans array. Or it could be somewhere else. I just can't figure it out for the life of me.

Edited Code:

public class TwentyFourGame {

    String [] ans = new String[20];
    boolean [] used = new boolean[20];
    int count = 0;
    int value = 0;

    public void Solve(double w, double x, double y, double z){
        double [] nums = {w,x,y,z};
        double eHold=0, fHold=0;

        //Replaces null array elements with empty string to avoid NPE
        for(int d=0; d<ans.length;d++){
            ans[d] = "";
        }

        for (int a=0;a< 4; a++){
            for (int b=0;b< 3; b++){
                for (int c=0;c<2; c++){
                    fHold = nums[2]+nums[3];
                    if (((nums[0]/nums[1])*fHold)==24)
                        append (nums[0]+" / "+nums[1]+" * ("+nums[2]+" + "+nums[3]+")" + " = 24");
                    else if (((nums[0]/nums[1])-fHold)==24)
                        append (nums[0]+" / "+nums[1]+" - ("+nums[2]+" + "+nums[3]+")" + " = 24");
                    else if (((nums[0]*nums[1])-fHold)==24)
                        append (nums[0]+" * "+nums[1]+" - ("+nums[2]+" + "+nums[3]+")" + " = 24");
                    else if (((nums[0]*nums[1])/fHold)==24)
                        append (nums[0]+" * "+nums[1]+" / ("+nums[2]+" + "+nums[3]+")" + " = 24");
                    else if (((nums[0]-nums[1])*fHold)==24)
                        append (nums[0]+" - "+nums[1]+" * ("+nums[2]+" + "+nums[3]+")" + " = 24");
                    else if (((nums[0]-nums[1])/fHold)==24)
                        append (nums[0]+" - "+nums[1]+" / ("+nums[2]+" + "+nums[3]+")" + " = 24");
                    else value++;
                    fHold=nums[2]-nums[3];

                    if (((nums[0]/nums[1])*fHold)==24)
                        append (nums[0]+" / "+nums[1]+" * ("+nums[2]+" - "+nums[3]+")" + " = 24");
                    else if (((nums[0]/nums[1])+fHold)==24)
                        append (nums[0]+" / "+nums[1]+" + ("+nums[2]+" - "+nums[3]+")" + " = 24");
                    else if (((nums[0]*nums[1])+fHold)==24)
                        append (nums[0]+" * "+nums[1]+" + ("+nums[2]+" - "+nums[3]+")" + " = 24");
                    else if (((nums[0]*nums[1])/fHold)==24)
                        append (nums[0]+" * "+nums[1]+" / ("+nums[2]+" - "+nums[3]+")" + " = 24");
                    else if (((nums[0]+nums[1])*fHold)==24)
                        append (nums[0]+" + "+nums[1]+" * ("+nums[2]+" - "+nums[3]+")" + " = 24");
                    else if (((nums[0]+nums[1])/fHold)==24)
                        append (nums[0]+" + "+nums[1]+" / ("+nums[2]+" - "+nums[3]+")" + " = 24");
                    else value++;
                    fHold=nums[2]*nums[3];

                    if (((nums[0]/nums[1])-fHold)==24)
                        append (nums[0]+" / "+nums[1]+" * ("+nums[2]+" * "+nums[3]+")" + " = 24");
                    else if (((nums[0]/nums[1])+fHold)==24)
                        append (nums[0]+" / "+nums[1]+" + ("+nums[2]+" * "+nums[3]+")" + " = 24");
                    else if (((nums[0]-nums[1])+fHold)==24)
                        append (nums[0]+" - "+nums[1]+" + ("+nums[2]+" * "+nums[3]+")" + " = 24");
                    else if (((nums[0]-nums[1])/fHold)==24)
                        append (nums[0]+" - "+nums[1]+" / ("+nums[2]+" * "+nums[3]+")" + " = 24");
                    else if (((nums[0]+nums[1])-fHold)==24)
                        append (nums[0]+" + "+nums[1]+" - ("+nums[2]+" * "+nums[3]+")" + " = 24");
                    else if (((nums[0]+nums[1])/fHold)==24)
                        append (nums[0]+" + "+nums[1]+" / ("+nums[2]+" * "+nums[3]+")" + " = 24");
                    else value++;
                    fHold=nums[2]/nums[3];

                    if (((nums[0]-nums[1])*fHold)==24)
                        append (nums[0]+" - "+nums[1]+" * ("+nums[2]+" / "+nums[3]+")" + " = 24");
                    else if (((nums[0]-nums[1])+fHold)==24)
                        append (nums[0]+" - "+nums[1]+" + ("+nums[2]+" / "+nums[3]+")" + " = 24");
                    else if (((nums[0]*nums[1])+fHold)==24)
                        append (nums[0]+" * "+nums[1]+" + ("+nums[2]+" / "+nums[3]+")" + " = 24");
                    else if (((nums[0]*nums[1])-fHold)==24)
                        append (nums[0]+" * "+nums[1]+" - ("+nums[2]+" / "+nums[3]+")" + " = 24");
                    else if (((nums[0]+nums[1])*fHold)==24)
                        append (nums[0]+" + "+nums[1]+" * ("+nums[2]+" / "+nums[3]+")" + " = 24");
                    else if (((nums[0]+nums[1])-fHold)==24)
                        append (nums[0]+" + "+nums[1]+" - ("+nums[2]+" / "+nums[3]+")" + " = 24");
                    else value++;
                    fHold=nums[1]*nums[2];

                    if (((nums[0]-fHold)/nums[3])==24)
                        append (nums[0]+" - ("+nums[1]+" * "+nums[2]+") / "+nums[3] + " = 24");
                    else if (((nums[0]-fHold)+nums[3])==24)
                        append (nums[0]+" - ("+nums[1]+" * "+nums[2]+") + "+nums[3] + " = 24");
                    else if (((nums[0]/fHold)+nums[3])==24)
                        append (nums[0]+" / ("+nums[1]+" * "+nums[2]+") + "+nums[3] + " = 24");
                    else if (((nums[0]/fHold)-nums[3])==24)
                        append (nums[0]+" / ("+nums[1]+" * "+nums[2]+") - "+nums[3] + " = 24");
                    else if (((nums[0]+fHold)/nums[3])==24)
                        append (nums[0]+" + ("+nums[1]+" * "+nums[2]+") / "+nums[3] + " = 24");
                    else if (((nums[0]+fHold)-nums[3])==24)
                        append (nums[0]+" + ("+nums[1]+" * "+nums[2]+") - "+nums[3] + " = 24");
                    else value++;
                    fHold=nums[1]-nums[2];

                    if (((nums[0]*fHold)/nums[3])==24)
                        append (nums[0]+" * ("+nums[1]+" - "+nums[2]+") / "+nums[3] + " = 24");
                    else if (((nums[0]*fHold)+nums[3])==24)
                        append (nums[0]+" * ("+nums[1]+" - "+nums[2]+") + "+nums[3] + " = 24");
                    else if (((nums[0]/fHold)+nums[3])==24)
                        append (nums[0]+" / ("+nums[1]+" - "+nums[2]+") + "+nums[3] + " = 24");
                    else if (((nums[0]/fHold)*nums[3])==24)
                        append (nums[0]+" / ("+nums[1]+" - "+nums[2]+") * "+nums[3] + " = 24");
                    else value++;
                    fHold=nums[1]/nums[2];

                    if (((nums[0]-fHold)*nums[3])==24)
                        append (nums[0]+" - ("+nums[1]+" / "+nums[2]+") * "+nums[3] + " = 24");
                    else if (((nums[0]-fHold)+nums[3])==24)
                        append (nums[0]+" - ("+nums[1]+" / "+nums[2]+") + "+nums[3] + " = 24");
                    else if (((nums[0]*fHold)+nums[3])==24)
                        append (nums[0]+" * ("+nums[1]+" / "+nums[2]+") + "+nums[3] + " = 24");
                    else if (((nums[0]*fHold)-nums[3])==24)
                        append (nums[0]+" * ("+nums[1]+" / "+nums[2]+") - "+nums[3] + " = 24");
                    else if (((nums[0]+fHold)*nums[3])==24)
                        append (nums[0]+" + ("+nums[1]+" / "+nums[2]+") * "+nums[3] + " = 24");
                    else if (((nums[0]+fHold)-nums[3])==24)
                        append (nums[0]+" + ("+nums[1]+" / "+nums[2]+") - "+nums[3] + " = 24"); 
                    else value++;
                    fHold=nums[1]+nums[2];

                    if (((nums[0]*fHold)/nums[3])==24)
                        append (nums[0]+" * ("+nums[1]+" + "+nums[2]+") / "+nums[3] + " = 24");
                    else if (((nums[0]*fHold)-nums[3])==24)
                        append (nums[0]+" * ("+nums[1]+" + "+nums[2]+") - "+nums[3] + " = 24");
                    else if (((nums[0]/fHold)-nums[3])==24)
                        append (nums[0]+" / ("+nums[1]+" + "+nums[2]+") - "+nums[3] + " = 24");
                    else if (((nums[0]/fHold)*nums[3])==24)
                        append (nums[0]+" / ("+nums[1]+" + "+nums[2]+") * "+nums[3] + " = 24");
                    else value++;

                    if (value == 192){
                        append("There is no solution for this set of numbers");

                        this.count ++;
                    }
                    // 0=a 1=b 2=c 3=d
                    eHold=nums[2];
                    nums[2]=nums[3];
                    nums[3]=eHold;
                }
                eHold=nums[1];
                nums[1]=nums[2];
                nums[2]=nums[3];
                nums[3]=eHold;
            }
            eHold=nums[0];
            nums[0]=nums[1];
            nums[1]=nums[2];
            nums[2]=nums[3];
            nums[3]=eHold;

            for (int j=0; j<ans.length;j++){
                if (ans[j] != "")
                    System.out.println(ans[j]);
            }
        }
    }


    //Method used to check if there are duplicates in the array of equations
    public void append(String equation){
        String text = equation;

        for (int e=0;e<used.length;e++){
            if (used[e]==false){
                ans[e] = text;
                used[e] = true;
                break;
            }
        }

        //Check if elements in the array are the same
        for (int c=0;c<ans.length;c++){
            for (int d = 0; d < ans.length; d++) {
                //if elements are the same do nothing
                if (ans[c].equals(ans[d])){
                    ans[d] = "";
                }
            }
        }
    }


    public static void main(String[]args){
        java.util.Scanner input = new java.util.Scanner(System.in);
        System.out.println("Enter 4 numbers between 1 - 9");
        double w,x,y,z;
        TwentyFourGame Player1 = new TwentyFourGame();
        w = input.nextDouble();
        x = input.nextDouble();
        y = input.nextDouble();
        z = input.nextDouble();
        input.close();
        Player1.Solve(w,x,y,z);
    }
}

Answer 1

1. double input? are you sure you don't want to use int?

2. you does not print any result into console. just try to find all System.out.println(...) statements.

    int value = 0; if (value == 192){ // <== Here value == 0, so this condition is always FALSE. And print never happens. for (int i=0; i<ans.length;i++){ System.out.println(ans[i]); } } 

Answer 2

I suspect your logic is wrong, which is why you're never hitting the append(String) method. If you debug it, you'll see that value only ever reaches 32, not the 192 that you're expecting.

Also, once you do hit the append method (try 1,1,3,7), you get a NullPointerException when you try to evaluate ans[c].equals(ans[d]) because ans[c] is null.