Morgan and a String HackerRank

Java

import java.util.*;
	public class MorganAndString {
	public static void main(String[] args) {
	Scanner in = new Scanner(System.in);
	int t = in.nextInt();
	in.nextLine();
	while(t-- > 0) {
	String A = in.nextLine();
	String B = in.nextLine();
	int i = 0, j = 0;
	StringBuffer sb = new StringBuffer();
	while(i < A.length() && j < B.length()) {
	if (A.charAt(i) < B.charAt(j)) {
	sb.append(A.charAt(i++));
	} else if (A.charAt(i) > B.charAt(j)) {
	sb.append(B.charAt(j++));
	} else {
	int x = i, y = j;
	char a = A.charAt(i);
	for(; x < A.length() && y < B.length(); x++, y++) {
	if (A.charAt(x) != B.charAt(y)) {
	break;
	} else if (A.charAt(x) > a) {
	sb.append(A.substring(i, x)).append(B.substring(j, y));
	i = x; j = y;
	a = A.charAt(x);
	}
	}
	if (x == A.length()) {
	sb.append(B.charAt(j));
	j++;
	} else if (y == B.length()) {
	sb.append(A.charAt(i));
	i++;
	} else {
	if (A.charAt(x) < B.charAt(y)) {
	sb.append(A.charAt(i));
	i++;
	} else {
	sb.append(B.charAt(j));
	j++;
	}
	}
	}
	}
	sb.append(A.substring(i)).append(B.substring(j));
	System.out.println(sb);
	}
	}
	}