模拟实现String类中的indexOf方法

package com.test5;

public class Test2 {
	
	public static void main(String[] args) {
		
		//返回子串sub在s中第一次出现的位置，如果没找到返回-1
		String s ="aasaewqewqeqw";
		String sub="ewq";
		System.out.println(IndexOf(s, sub));
		
	}

	public static int IndexOf(String s, String sub) {
		char[] sChars = s.toCharArray();
		char[] subChars = sub.toCharArray();
		int sLength = s.length();
		int subLength = sub.length();

		int sIndex = 0;
		int subIndex = 0;
		while (sIndex < sLength && subIndex < subLength) {
			if (sChars[sIndex] == subChars[subIndex]) {
				subIndex++;
				sIndex++;
			} else {
				sIndex = sIndex - subIndex + 1;
				subIndex = 0;
			}
		}

		int index = subIndex == subLength ? (subLength > 1 ? sIndex - subLength : sIndex - 1) : -1;
		return index;
	}

}