Dynamically growing array in Java

GrowingArray.java

public class GrowingArray
{
	Object[] array;
	int count;
	int capacity;

	public void appending(Object obj)
	{
		// grow array if needed
		if (count == capacity)
		{
			int i, newLen = capacity + 3;	/* 3 is an arbitrary increment here */
			Object[] newArray = new Object[newLen];
			for (i = 0; i < count; ++i)	// copy items
			{
				newArray[i] = array[i];
			}
			array = newArray;
		}

		array[count] = obj;
		++count;
	}
}

Generally, it is recommended to use System.arraycopy as it's faster than iterating over individual elements.

So I tried my hand at writing an extension to this that handles growing, shrinking, adding and removing. Busy learning Java so excuse me if the code sucks, what do you think?
`
public class DynamicArray {

public Object[] arr = {};

public void push(Object obj){
    growArr(arr.length);
    arr[arr.length-1] = obj;
}

public void set(Object obj, int index){
    if(arr.length < index){
        growArr(index);
    }
    arr[index] = obj;
}

public void remove(int index){
    arr[index] = null;
    shrinkArr();
}

public void shrinkArr(){
    int totalNotNull = 0;
    for(int i = 0; i < arr.length; i++) {
        if(arr[i] != null)
            totalNotNull++;
    }
    Object[] tempArr = new Object[totalNotNull];
    int currentPos = 0;
    for(int i = 0; i < arr.length; i++) {
        if(arr[i] != null){
            tempArr[currentPos] = arr[i];
            currentPos++;
        }
    }
    arr = new Object[totalNotNull];
    System.arraycopy(tempArr,0,arr,0,tempArr.length);
    tempArr = null;
}


public void growArr(int newSize){
    System.out.println("Current: " + arr.length + ", New: " + newSize);
    if(arr.length > 0){
        Object[] tempArr = new Object[(newSize)];
        System.arraycopy(arr,0,tempArr,0,arr.length);
        arr = new Object[(newSize+1)];
        System.arraycopy(tempArr,0,arr,0,tempArr.length);
        tempArr = null;
    }
    else{
        arr = new Object[1];
    }
}

public void readOutArray(){
    for(int i = 0; i < arr.length; i++){
        System.out.println("Arr "+i+":"+arr[i]);
    }
}

}

`