JAVA在文本文件中查找字符

import java.io.FileReader;

public class TestFile {

 public static void main(String[] args) {
  
  try{
   int i = 0;
   String str = "";
   FileReader fr = new FileReader("f://aaa.txt");
   
   char[] ch = new char[1024];
   
   while(fr.read(ch, 0, 1024) != -1){
    str += new String(ch);
    ch = new char[1024];
   }
   
   str += new String(ch);

   while((i = str.lastIndexOf("我")) != -1){
    System.out.println("我位于---" + i);
    str = str.substring(0, i);
   }

  }catch(Exception e){
   e.printStackTrace();
  }
 }
}