java.lang.StringIndexOutOfBoundsException: String index out of range: 12

import java.util.Scanner;public class homework3 {    public static void main(String[] args){        Scanner sc=new Scanner(System.in);        System.out.println("输入一段字符：");        String words=sc.next();        System.out.println("输入要查找的字符串：");        String toBeFound=sc.next();        int[] index=new int[10];                 //存放下标位置的数组index        int count=0;                             //index数组元素下标计数        if(toBeFound.length()==1){            for(int i=0;i<words.length();i++){   //如果输入的是字符                if(words.substring(i,i+1).equals(toBeFound)){                    index[count]=i;                    count++;                }            }        }else if(toBeFound.length()>1){            for(int i=0;i<words.length();i++){   //如果输入的字符串且长度>1                if(words.substring(i,i+toBeFound.length()).equals(toBeFound)){//26行错误                    index[count]=i;                    count++;                }            }        }        System.out.println("“"+toBeFound+"”"+"出现的位置是：");        for(int i=0;i<index.length;i++){            if(index[i]!=999999999){            //未赋新值的index中的元素消去                System.out.print(index[i]+" ");            }        }    }}