IO流读写文本文件

 import java.io.BufferedReader;
import java.io.FileReader;

public class ReadFile {
 FileReader reader = null;
 String filePath = "";
 BufferedReader br = null;
 
 public ReadFile(String filePath) throws Exception{
  this.filePath = filePath;
  reader = new FileReader(filePath);
  br = new BufferedReader(reader);   
 }
 
 public void initReader() throws Exception{
  reader = new FileReader(filePath);
  br = new BufferedReader(reader);  
 }
 //读文件的一行
 public String readLine() throws Exception{
  String lineString = "";
  if((lineString = br.readLine()) != null){
   return lineString;
  }
  return null;
 }
 //读整个文件
 public String readFileToString() throws Exception{
  String lineString = "";
  StringBuffer buffer = new StringBuffer();
  while((lineString = br.readLine()) != null){
   buffer.append(lineString).append("/n");
  }
  return buffer.toString();
 }
 
 public void closeReader() throws Exception{
  br.close();   
     reader.close();
 }

 public String getFilePath() {
  return filePath;
 }

 public void setFilePath(String filePath) {
  this.filePath = filePath;
 }

 //写文件

 public static void write(String path, String content) {
       String s = new String();
       String s1 = new String();
       try {
        File f = new File(path);
        if (f.exists()) {
         System.out.println("文件存在");
        } else {
         System.out.println("文件不存在，正在创建...");
         if (f.createNewFile()) {
          System.out.println("文件创建成功！");
         } else {
          System.out.println("文件创建失败！");
         }

        }
        BufferedReader input = new BufferedReader(new FileReader(f));

        while ((s = input.readLine()) != null) {
         s1 += s + "/n";
        }
        System.out.println("文件内容：" + s1);
        input.close();
        s1 += content;

        BufferedWriter output = new BufferedWriter(new FileWriter(f));
        output.write(s1);
        output.close();
       } catch (Exception e) {
        e.printStackTrace();
       }
 }

}