I updated it into like this.

                for(int c=top;c<anNumber[i];c--){
                    if(find == anNumber[c]){
                        output += anLetters[c] + "|";
                        System.out.print(output);
                    }
                }       

The problem now is The error is "java.lang.ArrayIndexOutOfBoundsException: 26". oh gosh. x.x

So at first I just copied the code in this program.

import java.io.BufferedReader;

import java.io.InputStreamReader;

import java.io.IOException;

 

public class ArrayStacks

{

public static void main(String[] args)

{

BufferedReader dataln=new BufferedReader (new InputStreamReader(System.in));

String c="", data="";

String[] arrays = new String[5];

int top=-1, b=0;

 

do{

System.out.println("Stack Main Menu");

System.out.println("\n1. Push");

System.out.println("2. Pop");

System.out.println("3. Stack Top");

System.out.print("?: ");

 

try{

c=dataln.readLine();

}

catch( IOException e ){

System.out.println("WRONG");

}

 

b=Integer.parseInt(c);

 

if(b==1){ //stack push

if(top==4){//stack full

System.out.println("\n");

System.out.println("Stack Overflow ");

}

else{

System.out.println("\n");

System.out.println("Stack Push ");

System.out.print("?: ");

try{

data=dataln.readLine();

}

catch( IOException e ){

System.out.println("WRONG");

}

top++;


arrays[top]=data;

System.out.println("\nStack");

System.out.println("");

for(int i=top; i>=0; i--){

System.out.println("" + arrays[i]);

}

}

}

System.out.println("\n\n");

}while(b!=4);

 

}

}

My code is

       top = -1;
       anNumber[0]=1;
            for(i=0;i<anNumber.length;i++){
                anNumber[i]=i+1;
            }
            
        do{
                System.out.println("\n\nPlease enter your choice from the following menu:");
                System.out.println("1. Enter number");
                System.out.println("2. Exit");
                choice = Integer.parseInt(reader.readLine());
                top++;
            switch (choice){
                case 1:
                System.out.print("Enter number: ");
                find=Integer.parseInt(reader.readLine());
                for(i=top;i<anNumber[i];i--){
                    if(find == anNumber[i]){
                        output += anLetters[i] + "|";
                        System.out.print(output);
                    }
                }       
                case 2:
                break;
            }   
        }while (choice > 0 && choice < 2);

The error is "java.lang.ArrayIndexOutOfBoundsException: -1".

So I'm still trying on it but I still have an error.

       String a;
       top = -1;
       anNumber[0]=1;
            for(i=0;i<anNumber.length;i++){
                anNumber[i]=i+1;
            }
            
        do{
                System.out.println("\n\nPlease enter your choice from the following menu:");
                System.out.println("1. Enter number");
                System.out.println("2. Exit");
                choice = Integer.parseInt(reader.readLine());
                top++;
            switch (choice){
                case 1:
                System.out.print("Enter number: ");
                find=Integer.parseInt(reader.readLine());
                
                for(i=top;i<=anNumber.length;i--){
                    if(find == anNumber[i]){
                        output += anLetters[i] + "|";
                        System.out.print(output);
                    }
                }       
                case 2:
                break;
            }   
        }while (choice > 0 && choice < 2);

It says out of bound.

Yeah. Thanks for that anyway. The problem. It's adding the new on on the bottom.

The output:
|B|

Next will be a:
|B|a|

It should be like this:
|a||B|

Thank you for your big help GregBrannon!