java实现求两个字符串最长公共子串的方法

import java.util.Scanner;
public class Main {
 public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  Main mainObj = new Main();
  int len = mainObj.getCommonStrLength(sc.next(),sc.next());
  System.out.println(len);
 }
 int getCommonStrLength(String str1, String str2) {
   str1 = str1.toLowerCase(); 
   str2 = str2.toLowerCase(); 
   int len1 = str1.length(); 
   int len2 = str2.length(); 
   String min = null; 
   String max = null; 
   String target = null;
   min = len1 <= len2 ? str1 : str2;
   max = len1 > len2 ? str1 : str2;
   //最外层：min子串的长度，从最大长度开始
   for (int i = min.length(); i >= 1; i--) {
    //遍历长度为i的min子串，从0开始
    for (int j = 0; j <= min.length() - i; j++) { 
     target = min.substring(j, j + i); 
     //遍历长度为i的max子串，判断是否与target子串相同，从0开始
     for (int k = 0; k <= max.length() - i; k++) { 
      if (max.substring(k,k + i).equals(target)) { 
       return i; 
      }
     }
    }
   } 
   return 0; 
 }
}