Java IO的一些列子

Write（）方法写入文件

public static void main(String[] args){
    try{
        BufferedWriter out = new BufferedWriter(new FileWriter("D:\temp\runoon.txt"));//创建文件
        out.write("cainiaojiaocheng");//向文件中写入字符串
        out.close();//关闭文件。运行之后查看目录下应该生成文件，并且文件中有写入的字符串
        System.out.println("create file successfully");
    }catch(IOException e){

    }

}

//用readLine()从文件中读取数据
try{
    BufferedReader in = new BufferedReader(new FileReader("D:\temp\runoon.txt"));//获取文件地址
    String str;//创建一个字符串对象来缓存下读出来的字符串
    while((str=in.readLine())!=null){
        System.out.print(str);
    }
}catch(IOException e){
    System.out.println(e);
}

创建临时文件，向文件中对家数据

import java.io.*;


/**
 * Created by Sandy.Liu on 2017/8/8.
 */
public class CreateTempFile {
    public static void main(String[] args){
        try {
            File fileDir = new File("D://Temp//");
            File tempFile = File.createTempFile("createTempFile", ".txt",fileDir);
            tempFile.deleteOnExit();
            BufferedWriter bw = new BufferedWriter(new FileWriter(tempFile));
            bw.write("String 1");
            bw.close();
            System.out.println("temp file is created");

            //向文件中追加数据，这里注意不要创建一个新的BufferedWriter对象，要用之前的对象，不然会再创建一个新的tempfile，而不是之前的那个对象追加
            bw = new BufferedWriter(new FileWriter(tempFile,true));
            bw.write("string 2");
            bw.close();
            BufferedReader br = new BufferedReader(new FileReader(tempFile));
            String str;
            while((str=br.readLine())!=null){
                System.out.println(str);
            }
            br.close();
        }catch (IOException e){
            System.out.println(e);
        }
    }
}
重命名

import java.io.*;

/**
 * Created by Sandy.Liu on 2017/8/8.
 */
public class FileRename {
    public static void main(String[] args){
     File oldName = new File("D://Temp//TestSource.txt");
     File newName = new File("D://Temp//TestSource1.txt");
     if(oldName.renameTo(newName)){
         System.out.println("rename successfully");
     }else{
         System.out.println("Error");
     }
    }
}

复制文件，用到BufferedWriter，BufferedReader,InputStream，OutputStream

import java.io.*;

/**
 * Created by Sandy.Liu on 2017/8/8.
 */
public class CopyFile {
    public static void main(String[] args){
        try {
            //创建文件，并向文件中写入数据
            BufferedWriter bf = new BufferedWriter(new FileWriter("D://Temp//TestSource.txt"));
            bf.write("this is for test copy files from TestSource.txt to TestTarget.txt");
            bf.close();

            //读出文件到buffer里，为写入另一个文件做准备
            InputStream is = new FileInputStream(new File("D://Temp//TestSource.txt"));
            byte[] buf = new byte[1024];

            //把buffer里的数据写入到目标文件中去
            OutputStream ot = new FileOutputStream(new File("D://Temp//TestTarget.txt"));
            int len;
            while((len=is.read(buf))>0){
                ot.write(buf,0,len);
            }

            //从目标文件中读取字符串，输出到控制台
            BufferedReader br = new BufferedReader(new FileReader("D://Temp//TestTarget.txt"));
            String str;
            while((str=br.readLine())!=null){
                System.out.println(str);
            }
        }catch(IOException e){
            System.out.println(e);
        }
    }
}