怎么判断一个字符串是另一个的子串

package lmj.zdsoft.efforts.string;

/*
 * 判断字符串包含关系 及String一些用法
 *
 */

public class xx {

 public static boolean getBoo(String str1, String str2) {
  boolean b = false;

  if (str1.length() > str2.length()) {
   int i = str1.indexOf(str2);
   if (i > 0) {
    return true;
   } else {
    return b;
   }

  } else {
   int i = str2.indexOf(str1);
   if (i > 0) {
    return true;
   } else {
    return b;
    //newInstance();  
   }

  }
 }

 public static void main(String[] avb) {
  //法一
  String a = "1232456789";
  String b = "876";
  boolean c = getBoo(a, b);
  if (c == true) {
   System.out.print("OK");
  } else {
   System.out.print("NO");
  }
  
  //法二
  String fatherString = "I love you lmj";

  String sonString = "lmj";
  if(fatherString.contains(sonString))
     System.out.println("the relation is father and son");

 }
}