java 学习笔记

java 文件操作

1、从文件读取数据并打印到控制台

import java.io.FileInputStream;
import java.io.FileNotFoundException;

public class File {

    /**
     * @param args
     * @throws FileNotFoundException
     */
    public static void main(String[] args){
        // TODO Auto-generated method stub
        byte[] buff = new byte[5];
        try {
            FileInputStream fileinputstream = new FileInputStream("c://1.txt");
            while (fileinputstream.read(buff) != -1){
                System.out.write(buff);
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

2、写文件

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;

public class Fileoutput {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        try {
            FileOutputStream fileOutputStream = new FileOutputStream("c://1.txt");
            PrintStream printStream = new PrintStream(fileOutputStream);
            printStream.println("i'm fine!");
            printStream.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


    }

}

3、文件拷贝

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;

public class Copy {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        byte[] buff = new byte[100];
        int n;
        try {
            FileOutputStream fileOutputStream = new FileOutputStream("c://2.txt");
            FileInputStream fileInputStream = new FileInputStream("c://1.txt");
            while ((n = fileInputStream.read(buff)) != -1){
                fileOutputStream.write(buff);
            }
            fileInputStream.close();
            fileOutputStream.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

4、按行读取并显示

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

public class Fileline {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        try {
            FileReader fileReader = new FileReader("c://1.txt");
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            String content;
            int count = 0;
            while ((content = bufferedReader.readLine()) != null){
                count++;
                System.out.print("第"+count+"行:"+content+"\n");
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


    }

}

5、随机访问文件

import java.io.FileNotFoundException;
import java.io.RandomAccessFile;
import java.util.RandomAccess;

public class FileAccess {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        try {
            RandomAccessFile accessFile = new RandomAccessFile("c://1.txt", "rw");
            accessFile.seek(accessFile.length());
            accessFile.writeBytes(" ok");
            accessFile.seek(0);
            System.out.print(accessFile.readLine());

        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }


    }

}