import java.io.*;

import java.util.*;

public class test {

    public void test_readfile(String filePath){

        File file = new File(filePath);

        FileReader fr = null;

        BufferedReader reader = null;

        try{

            fr = new FileReader(file);

            reader = new BufferedReader(fr);

            String tmpString = "";

            while((tmpString = reader.readLine()) != null){

                System.out.println(tmpString);

            }

        }

        catch (FileNotFoundException e){

            e.printStackTrace();

        }

        catch (IOException e){

            e.printStackTrace();

        }

        finally {

            try{

                reader.close();

                fr.close();

            }

            catch (IOException e){

                e.printStackTrace();

            }

        }

    }

    public static void main(String []args){

        test case1 = new test();

        String filePath = "D:\\test.txt";

        case1.test_readfile(filePath);

    }

}

import java.io.*;

import java.util.*;

public class test {

    public void test_writefile(String filePath){

        File file = new File(filePath);

        FileWriter fw = null;

        BufferedWriter writer = null;

        try{

            fw = new FileWriter(file);

            writer = new BufferedWriter(fw);

            writer.write("hello");

            writer.newLine(); //换行

            writer.flush();

            writer.write("123");

            writer.newLine();

        }

        catch(FileNotFoundException e){

            e.printStackTrace();

        }

        catch (IOException e){

            e.printStackTrace();

        }

        finally {

            try{

                writer.close();

                fw.close();

            }

            catch (IOException e){

                e.printStackTrace();

            }

        }

    }

    public static void main(String []args){

        test case1 = new test();

        String filePath = "D:\\test.txt";

        case1.test_writefile(filePath);

    }

}