Longest Common Subsequence in java

LongestCommonSubsequence.java

import java.time.Duration;
import java.time.Instant;

public class LongestCommonSubsequence {
    public int lcsRecursive(char[] a, char[] b, int i, int j) {
        if (a.length == i || b.length == j)
            return 0;
        else if (a[i] == b[j])
            return 1 + lcsRecursive(a, b, i + 1, j + 1);
        else
            return Math.max(lcsRecursive(a, b, i + 1, j), lcsRecursive(a, b, i, j + 1));
    }

    public int lcsMemoization(char[] a, char[] b) {
        int m = a.length;
        int n = b.length;
        int l[][] = new int[m + 1][n + 1];

        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                if (a[i-1] == b[j-1])
                    l[i][j] = l[i-1][j-1] + 1;
                else
                    l[i][j] = Math.max(l[i-1][j], l[i][j-1]);
            }
        }
        return l[m][n];
    }

    public static void main(String[] args) {
        var a = "mhunuzqrkzsnidwbun";
        var b = "szulspmhwpazoxijwbq";
        calculateRecursively(a, b);
        calculateWithMemoization(a, b);
        a = "AGGTAB";
        b = "GXTXAYB";
        calculateRecursively(a, b);
        calculateWithMemoization(a, b);
    }

    private static void calculateRecursively(String a, String b) {
        var lcs = new LongestCommonSubsequence();
        var start = Instant.now();
        int r = lcs.lcsRecursive(a.toCharArray(), b.toCharArray(), 0, 0);
        var end = Instant.now();
        var duration = Duration.between(start, end);
        System.out.println(String.format("LCS (recursive) for %s and %s is %d", a, b, r));
        System.out.println("Time spent: " + duration);
    }

    private static void calculateWithMemoization(String a, String b) {
        var lcs = new LongestCommonSubsequence();
        var start = Instant.now();
        int r = lcs.lcsMemoization(a.toCharArray(), b.toCharArray());
        var end = Instant.now();
        var duration = Duration.between(start, end);
        System.out.println(String.format("LCS (memoization) for %s and %s is %d", a, b, r));
        System.out.println("Time spent: " + duration);
    }
}