collections - Building a bag class in Java

Question

I'm in dire need of help with this project. I'm trying to implement a Bag class for a programming assignment, and I'm getting hung up on the addAll(), Union(), and equals(), methods.

Edit: According to the assignment, addAll() is supposed to add all of the the objects from the second array into the first. I'm no longer getting an error when I run it, but for some reason it will not add all of the elements from the second array, it will only add the first 2. Thanks guys, this one is working perfectly now!

Edit: For Union(), I'm supposed to create a third bag that will contain all the contents of the first 2 bags. I was getting an ArrayIndexOutOfBoundsException when running this method. I've updated the code following biddulph.r and it's also working great. Thanks again!

Edit: "First attempt" And for equals(), it's supposed to check the size of the bags to make sure they are equal in size, then check to see if they contain the same numbers. So as it's written now, my equals() method will compare sizes and return the boolean value for that, but I'm unsure of how to make it compare the actual values.

import java.util.Arrays;
import javax.swing.*;

public class bag {
  int maxSize = 10; //Size of the arrays
  int count = 0; //Number of items stored in the array
  int[] a;
  int[] b;
  bag c;
  bag d;

  public bag() {
    //for(int i = 0; i < maxSize; i++){
    //a[i] = (int)(1+Math.random()*100);
    //}
    a = new int[maxSize];
  }

  public String bagString() {
    return Arrays.toString(a);
  }

  public void add(int b) {
    try {
      a[count] = b;
      count++;
    } catch (ArrayIndexOutOfBoundsException n) {
      JOptionPane.showMessageDialog(null, "Array is full, element will not be added");
    }
  }

  public void removeRandom() {
    int i = (int)(1 + Math.random() * (count - 1));
    a[i] = a[count - 1];
    a[count - 1] = 0;
    count--;
  }

  public void remove(int b) {
    for (int i = 0; i < maxSize; i++) {
      if (contains(b)) {
        a[i] = a[count - 1];
      }
    }
  }

  public boolean isEmpty() {
    if (count == 0) return true;
    else return false;
  }

  public boolean contains(int b) {
    int tf = 0;
    for (int i = 0; i < maxSize; i++) {
      if (a[i] == b) tf = 1;
    }
    if (tf == 1) return true;
    else return false;
  }

  public int size() {
    return count;
  }

  public void addAll(bag c, bag d) {
    if (a.length >= c.size() + d.size()) {
      for (int i = 0; c.size() <= d.size(); i++) {
        c.add(d.a[i]);
      }
    }
  }

  public void union(bag c, bag d) {
    bag bigger = new bag();
    for (int i = 0; i < c.size(); i++) {
      bigger.add(c.a[i]);
    }
    for (int i = 0; count < d.size() - 1; i++) {
      bigger.add(d.a[i]);
    }
    System.out.println(bigger.bagString());
  }

      public boolean equals(bag c, bag d){

        if(c.size() != d.size()){

                return false;

        }else{

                for(int i = 0; i < c.union(c, d).size(); i++){

                        if(c.union(c, d).contains(c.a[i]) && c.union(c, d).contains(d.a[i])){

                        return true;                                   
                        }                              

                }              
                    return false;                              
        }

    }

}

I really appreciate any help you guys can give me, thanks.

EDIT: Thanks to everyone for your help, you guys are life savers.

Answer 1

Your problem for addAll() is here

   if (a.length >= c.size() + d.size()) {

        for (int i = 0; c.size() <= d.size(); i++) {
            c.add(d.a[i]);
        }
   }

You shouldn't be adding elements until your c bag becomes bigger than d, you should be adding all of d's elements to c.

for (int i = 0; i < d.size(); i++) {
    c.add(d.a[i]);
}