Grouping identical numbers in an Array List ( Big Java Ex 7.5)

Question

I'm having a bit of trouble figuring out how I should approach this problem even with some pseudo code that the book gives as hints ( This chapter is about arrays and arrayLists). By the way this isn't homework, and I am self learning.

Problem

A run is a sequence of adjacent repeated values. Write a program that generates a sequence of 20 random die tosses and that prints the die values, marking the runs by including them in parentheses, like this: 1 2 (5 5) 3 1 2 4 3 (2 2 2 2) 3 6 (5 5) 6 3 1

Hint in Book

Set a boolean variable inRun to false.

For each valid index i in the array list If inRun

If values[i] is different from the preceding value Print ) inRun = False Else

If values[i] is the same as the following value Print ( inRun = True Print Values; [i]

What I don't get is how the hint is really helping. Say we have multiple numbers like 2 2 2 2 Wont this just do something like (2 2) 2 2

Heres what I am trying so far

import java.util.ArrayList;
import java.util.Random;
class seq
{
    private ArrayList<Integer> nums;
    private Random randNum;
    private boolean inRun;
    public seq()
    {
        nums = new ArrayList<Integer>();
        randNum = new Random();
        inRun = false;
    }
    
    public void addToArrList()
    {
        for(int i = 0; i < 20 ; i++)
        {
            int addThisNum = randNum.nextInt(20)+1;
            nums.add(addThisNum);
        }
    }
    
    public void checkSides()
    {
        int count = 0;
        for(int i = 0 ; i < nums.size(); i++)
        {
            if(nums.get(i) != nums.get(i-1))
            {
                inRun = false;
            }
            if(nums.get(i) == nums.get(i+1))
            {
                inRun = true;
            }
        }
    }
    
    public String toString()
    {
        String output = "Array is:";
        if (output.)
    }
}

ANOTHER ATTEMPT

import java.util.Random;
import java.util.ArrayList;
class Seq
{
    private ArrayList<Integer> nums;
    private Random randNum;
    public Seq()
    {
        nums = new ArrayList<Integer>();
        randNum = new Random();
    }
    public void fillArrList()
    {
        for (int i = 0 ; i < 20 ; i++)
        {
            int thisRandNum = randNum.nextInt(20)+1;
            nums.add(thisRandNum);
        }
    }
    
    public String toString() {
        StringBuilder result = new StringBuilder();
        boolean inRun = false;
        for (int i = 0; i < nums.size(); i++) {
            if (i < nums.size() - 1 && nums.get(i).equals(nums.get(i + 1))) {
                if (!inRun) {
                    result.append("(");
                }
                result.append(nums.get(i));
                inRun = true;

            } else {
                result.append(nums.get(i));
                if (inRun) {
                    result.append(")");
                }
                inRun = false;

            }
        }
        return result.toString();
    }
}

public class Sequence{
    public static void main(String [] args)
    {
        Seq seqObj = new Seq();
        seqObj.fillArrList();
        System.out.println(seqObj.toString());
    }
}

OUTPUT

85641520612614320473181113612

201362181920141020(1919)514920162914

ETC

Answer 1

I think they mean something like this:

@Override
public String toString() {
    StringBuilder result = new StringBuilder();
    boolean inRun = false;
    for (int i = 0; i < nums.size(); i++) {
        if (i < nums.size() - 1 && nums.get(i).equals(nums.get(i + 1))) {
            if (!inRun) {
                result.append("(");
            }
            result.append(nums.get(i));
            inRun = true;

        } else {
            result.append(nums.get(i));
            if (inRun) {
                result.append(")");
            }
            inRun = false;

        }
    }
    return result.toString();
}

Also you probably want to generate Randoms between 1 and 6, i.e.

int addThisNum = randNum.nextInt(6) +1; 

Answer 2

Here randNum.nextInt(20)+1; you are generating a random value from 0 to 20 you need to generate a random value which need to contain only one digits,

in the for loop i begin with zero in the first condition you call nums.get(i-1) which is incorrect as i = 0 so i-1 will be -1

There more logic issues you can check them from the code above

package com.run;

import java.util.ArrayList;
import java.util.Random;

public class Run {
    private ArrayList<Integer> nums;
    private Random randNum;
    private boolean inRun;
    private StringBuffer sb;
    public Run(){
         nums = new ArrayList<Integer>();
         randNum = new Random();
         inRun = false;
         sb = new StringBuffer();
    }
    public static void main(String[] args) {
        Run run = new Run();
        run.addToArrList();
        run.checkSides();
    }
    public void addToArrList()
    {
        for(int i = 0; i < 20 ; i++)
        {
            int addThisNum = randNum.nextInt(9)+1;
            nums.add(addThisNum);
        }
    }

    public void checkSides()
    {
        int count = 0;
        for(int i = 1 ; i < nums.size(); i++)
        {
            if(nums.get(i) != nums.get(i-1))
            {
                if(inRun)
                    sb.append(")");
                inRun = false;
            }
            else
            {
                if(!inRun){
                    System.out.println(nums.get(i));
                    inRun = true;
                    sb.replace(sb.length()-1, sb.length(), "(" + nums.get(i-1));
                }
            }
            sb.append(String.valueOf(nums.get(i)));
        }
        System.out.println(sb.toString());
    }
}