FilterN.java

/**
 * FilterN is an abstract class that extends Filter.  It
 * initializes an NBuffer which will store the last N inputs.
 * @author gmh73
 *
 * @param <T>
 */
public abstract class FilterN<T> extends Filter<T> {
	//The last N inputs
	protected NBuffer<T> buf;
	//The number of inputs since the output updated
	protected int inputsSinceNewOutput;
	//The number of inputs we are retaining
	public final int N;
	
	/**
	 * Sets the FilterN to size n.  The filter will remember n
	 * inputs.
	 * @param n		The number of inputs the filter will remember
	 */
	public FilterN(int n){
		checkN(n);
		buf = new NBuffer<T>(n);
		inputsSinceNewOutput = 0;
		N = n;
	}
	
	/**
	 * Checks if n is valid, ie >= 1
	 * @param n
	 */
	protected final void checkN(int n) {
		if(n <= 0)
			throw new IllegalArgumentException("N must be at least 1.");
	}
	
	/**
	 * Resets the previous output to r and sets the inputs
	 * since a new output to 0. So, if a child class relies on
	 * inputsSinceNewOutput to decide whether or not to update an output,
	 * it will not search its memory for at least N inputs.
	 */
	@Override
	public void reset(T r) {
		setOutput(r);
		inputsSinceNewOutput = 0;
	}
}