toString using generic variables?

Question

So there I have this Bag class here, to which I added a remove(T x) method, and now I want to print this, I know I have to use the toString() method but I keep getting either compilation error or still getting the hash code of the object b... there is my interpretation of this but still doesn't work, my solution (the particular) gives me error on the return bag[i] line :(

class Bag<T> {// generic class with T standing for a class

    private T[] bag =(T[])(new Object[100]);                 
    private int numElements = 0; // junk in bag[numElements..] 

    void add(T x) { // put x in bag
            bag[numElements] = x; numElements++;
    }

    void remove (T x){
        if(x!=null && numElements>0){
            for(int i = 0; i < numElements; i++){
                if(bag[i]==x){
                    bag[i]=bag[numElements];
                    numElements-=1;
                }
            }
        }
    }

    int freq(T x) { // how many x’s in bag?
            int count = 0;
            for (int i=0; i<numElements; i++)
                if (bag[i].equals(x)) // .equals because T a class 
                    count++;
            return count;
    }

    public String toString(){
        for(int i = 0; i < numElements; i++){
            return bag[i];
        }
    }
}

class GenericExample {
    public static void main(String[] args) {        
        Bag<String> b = new Bag<String>();
        b.add("cat"); b.add("dog"); b.add("cat"); 

    }
}

I also tried typing String.valueOf(bag[i])but still had compilation error... Why is there a problem anyway? In this example the T is a String so I can't understand why it's doing that..

Answer 1

do like this

public String toString(){
    return Arrays.toString(bag);
}

Answer 2

You want to change the toString method maybe in the following:

public String toString(){
    return Arrays.toString(bag);        
}

OR the home brew version

public String toString(){
    StringBuilder sb = new StringBuilder();
    for(int i = 0; i < numElements; i++){
        sb.append(bag[i]);
    }        
    return sb.toString();
}

If the object you put into your bag does not override toString, then you get a string of hashcodes.

Answer 3

What about using Arrays.toString():

public String toString(){
    return Arrays.toString(bag);
}

Answer 4

You cannot return an Object when String is expected.

Use return bag[i].toString()

Also

public String toString(){
    for(int i = 0; i < numElements; i++){
        return bag[i];
    }
}

You can return only once from the function. You cannot put return statement is loop. You can probably use StringBuilder to append all your data in the loop and the finally call toString() on it and return from outside the loop.

Answer 5

Why are you trying to return multiple times? Did you just want to concatenate all the index values like this?

public String toString(){
    StringBuilder sb = new StringBuilder();

    for(int i = 0; i < numElements; i++){
        sb.append(bag[i] + ", ");
    }

    return sb.toString();
}