java 文件操作

java读文件

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class ReaderTest1 {
    public static void main(String[] args) throws IOException{
        reader();
    }
    public static void reader() throws IOException {
        //定义一个指向c:\\x.txt的字节流
        FileInputStream fis = new FileInputStream("C:\\x.txt");
        //字节流转换成InputStreamReader
        InputStreamReader isr = new InputStreamReader(fis);
        //InputStreamReader 转换成带缓存的bufferedReader
        BufferedReader bufferedReader = new BufferedReader(isr);
        //将读取出来的信息赋值给字符串s
        String ss = new String();
        String s;
        while ((s = bufferedReader.readLine())!=null) {
            ss += s;
        }
        //定义一个指向输出的字节流
        FileOutputStream fos = new FileOutputStream("D:\\x.txt");
        //字节流转换成outputStreamWriter
        OutputStreamWriter osw = new OutputStreamWriter(fos);
        //outputStreamWriter 转换成带缓存的bufferedReader
        BufferedWriter bufferedWriter = new BufferedWriter(osw);
        bufferedWriter.write(ss);
        bufferedWriter.close();
        osw.close();
        fos.close();
        
    }
}

 追加内容

import java.io.FileOutputStream;
import java.io.IOException;

public class FileOutputStreamtrueTest {
    public static void fileInputStreamTest() throws IOException {
        String filename;
        filename = "C:\\a.txt";
        String hello = "hello java";
        FileOutputStream fos = new FileOutputStream(filename,true);
        byte b[] = hello.getBytes();
        fos.write(b);
        fos.close();
    }
    public static void main(String[] args) throws IOException {
        fileInputStreamTest();
    }
}