Thread: Expanding the capacity of an array

Hello all,
I declare an array of objects with a default capacity of 2 and I am trying to expand capacity once the limit is meet. I am calling the "expandCapacity" method which creates a new array of twice the old size and copies the old array into the new one. I get the following error:

"Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [LcharFreqNode;
at driver.main(driver.java:45)"

function call from main

 
if (count >= mycharFreqNode.length)
	    	  mycharFreqNode = arrayOps.expandCapacity(mycharFreqNode);

expandCapcity method

public class arrayOps<T> {
 
	public static <T> T[] expandCapacity(T[] data){
		T[] larger = (T[]) (new Object [data.length *2]);
 
		for (int index = 0; index < data.length; index++)
			larger[index] = data[index];
 
		data = larger;
		return larger;
		}
}

HW your comment is true, but using a integer will not work. Creating a new array of size Object doesn't contain enough space for an array of type Integer.

C makes tis sort of thing easy


Chris

Thank you for the replies.
myCharFreqNode is the type of an object I created. It is declared like this in main

charFreqNode mycharFreqNode[] = new charFreqNode[2];

The class definition of charFreqNode is below:

public class charFreqNode {
 
	//class data members
	char myChar;
	int myCharFreq;
 
	//constructor
	public <T> charFreqNode(T myChar, T myCharFreq)
	{
		this.myChar = (Character) myChar;
		this.myCharFreq = (Integer) myCharFreq;
	}
 
 
	public int compareTo(charFreqNode myNode)
	{
		int result = 0;
 
		if (this.myCharFreq < myNode.myCharFreq)
			result = -1;
 
		return result;
	}
	public String toString(int count)
	{
		String result = null;
		result = String.format( "Node #%d has character \"%c\" with a frequency \"%d.\"", count, this.myChar, this.myCharFreq);
		return result;
 
	}
 
}

Because arrays are fixed size, the rule of thumb is to only use arrays when you know in advance exactly how big they will need to be. For dynamic arrays, use ArrayList (or Vector if multi-threading).