Longest Common Subsequence Java Implementation

Recently I needed to implement LCS (Longest Common Subsequence) algorithm from dynamic programming for solving one of the problems. So I ended up writing quick implementation of LCS. For more details on LCS:
http://en.wikipedia.org/wiki/Longest_common_subsequence_problem

The algorithm referred from “Introduction to Algorithms” by T. Cormen et. al.

/*
 * LCSAlgorithm.java
 */

/**
 * <p>This is implementation of the famous "Longest Common Subsequence". It uses
 * dynamic programming approach to calculate the matrix of two strings based
 * on how many characters match. This is a core implementation which first 
 * computes the matrix based on the matching characters & assign weights in 
 * the incremental approach. After assigning weights it traverses through the
 * matrix to find all the matched characters. This longest common subsequence 
 * can be used in different ways based on the underlying implementation. This 
 * approach uses dynamic programming method and works in bottom up way to 
 * generate the suboptimal solution. </p>
 * 
 * @author rgandhi
 *
 */
public class LCSAlgorithm {
	
	/**
	 * <p>Calculates the length of longest common sequence.  The matrix is 
	 * calculated based on the matching characters between two strings &
	 * by assigning weights in each subsequent steps. </p>
	 * 
	 * @param source - Input data
	 * @param target - Entity to be matched
	 * @return - Matrix of weights.
	 */
	public int[][] calculateLength(final char[] source, 
			final char[] target) {
		int[][] matrix = new int[source.length+1][target.length+1];
		
		for (int i = 0; i < source.length; i++) {
			matrix[i][0] = 0;
		}
		for (int j = 0; j < target.length; j++) {
			matrix[0][j] = 0;
		}

		for(int i = 1; i < source.length; i++) {
			for(int j = 1; j < target.length; j++) {
                if (source[i-1] == target[j-1]) {
                	matrix[i][j] = matrix[i-1][j-1] + 1;
                } else if (matrix[i-1][j] >= matrix[i][j-1 ]) {
                	matrix[i][j] = matrix[i-1][j]; 
                } else {
            		matrix[i][j] = matrix[i][j-1];
            	} 
			}
		}
		return matrix;
	}
	
	/**
	 * <p>This function traverses through the matrix obtained in the earlier 
	 * step in recursive manner & appends the matched elements together and 
	 * hence returns the longest subsequence.</p>
	 * 
	 * @param builder - StringBuilder
	 * @param matrix - Weights between 2 strings
	 * @param source - Input data
	 * @param target - Entity to be matched
	 * @param i - Source counter
	 * @param j - Target counter
	 * @return - StringBuilder
	 */
	public StringBuilder constructLCS(StringBuilder builder, int[][] matrix, 
			final char[] source, final char[] target,int i, int j ) {
		
		if (i == 0 || j == 0) {
			return new StringBuilder();
		} else 	if (source[i-1] == target[j-1]) {
			constructLCS(builder, matrix, source, target, i-1, j-1);
			builder.append(target[j-1]);
		} else {
			if (matrix[i -1][j] > matrix[i][j -1]) {
				constructLCS(builder, matrix, source, target, i-1, j);
			} else {
				constructLCS(builder, matrix, source, target, i, j-1);
			}
		}
		
		return builder;
	}
}