Java之旅_高级教程_实例_文件操作

1.文件写入

import java.io.*;

public class MainClass{
    public static void main(String[] args){
        try{
            BufferedWriter out = new BufferedWriter(new FileWriter("testwrite.txt"));
            out.write("lalala");
            out.close();
            System.out.println("创建成功 ！");
        }catch(IOException e){
            e.printStackTrace();
        }        
    }
}

2.读取文件内容：

import java.io.*;

public class MainClass{
    public static void main(String[] args){
        try{
            BufferedReader rd = new BufferedReader(new FileReader("testwrite.txt"));
            String str;
            while((str=rd.readLine())!=null){
                System.out.println(str);
            }
            rd.close();
            System.out.println(str);
        }catch(IOException e){
            e.printStackTrace();
        }        
    }
}

3.删除文件(File类的delete()方法)

import java.io.*;

public class MainClass{
    public static void main(String[] args){
        try{
            File file = new File("D:/Workspace/sqldemo/testwrite.txt");
            if(file.delete()){
                System.out.println(file.getName()+"文件已删除");
            }else{
                System.out.println("文件删除失败");
            }
        }catch(Exception e){
            e.printStackTrace();
        }        
    }
}

4.将文件内容复制取另一个文件

import java.io.*;

public class MainClass{
    public static void main(String[] args) throws Exception{
        //向srcrile中写入数据
        BufferedWriter out1 = new BufferedWriter(new FileWriter("srcfile"));
        out1.write("string to be coped
");
        out1.close();
        //将数据从srcfile复制到destfile文件中，以1024个字节数据为单位复制
        InputStream in = new FileInputStream(new File("srcfile"));
        OutputStream out = new FileOutputStream(new File("destfile"));
        byte[] buf = new byte[1024];
        int len;
        while((len=in.read(buf)) >0){
            out.write(buf);
        }
        in.close();
        out.close();
        //以每行的方式读取destfile文件中数据
        BufferedReader in1 = new BufferedReader(new FileReader("destfile"));
        String str;
        while((str=in1.readLine())!=null){
            System.out.println(str);
        }
        in1.close();
    }
}

 5.向文件中追加数据

import java.io.*;

public class MainClass{
    public static void main(String[] args) throws Exception{
        BufferedWriter out = new BufferedWriter(new FileWriter("filename"));
        out.write("astring 1
");
        out.close();
        //true 追加   FileWriter构造方法
        out = new BufferedWriter(new FileWriter("filename",true));
        out.write("astring 2");
        out.close();
        
        BufferedReader in = new BufferedReader(new FileReader("filename"));
        String str;
        while((str = in.readLine())!=null){
            System.out.println(str);
        }
        in.close();
    }
}

6.创建临时文件

import java.io.*;

public class MainClass{
    public static void main(String[] args) throws Exception{
        File tmp = File.createTempFile("testtemp",".txt");
        System.out.println("文件路径"+tmp.getAbsolutePath());
        //终止后删除临时文件
        tmp.deleteOnExit();
        BufferedWriter out = new BufferedWriter(new FileWriter(tmp));
        out.write("astring");
        System.out.println("临时文件已创建:");
        out.close();
    }
}

7.修改文件最后的修改日期

import java.io.*;
import java.util.Date;

public class MainClass{
    public static void main(String[] args) throws Exception{
        File f = new File("c:/myjava.txt");
        f.createNewFile();
        //获取文件最后修改日期并打印出来
        Date ftime = new Date(f.lastModified());
        System.out.println(ftime.toString());
        //更改文件最后修改日期并打印出来
        System.out.println(f.setLastModified(System.currentTimeMillis()));
        ftime = new Date(f.lastModified());
        System.out.println(ftime.toString());        
    }
}

8.获取文件大小 ，使用File类的file.exists()和file.length()方法来获取文件大小 

public class MainClass{
    public static void main(String[] args) throws Exception{
        long size = getSize("c:/install.log");
        System.out.println("文件大小 为："+size);
    }
    public static long getSize(String filename){
        File file = new File(filename);
        if(!file.exists()||!file.isFile()){
            System.out.println("文件不存在");
            return -1;
        }
        return file.length();
    }
}

9.文件重命名

public class MainClass{
    public static void main(String[] args) throws Exception{
        File oldf = new File("c:/program.txt");
        oldf.createNewFile();
        File newf = new File("c:/java.txt");
        if(oldf.renameTo(newf)){
            System.out.println("已重命名");
        }else{
            System.out.println("error");
        }
    }
}

10.设置文件只读：f.setReadOnly()

public class MainClass{
    public static void main(String[] args) throws Exception{
        File f = new File("c:/java.txt");
        System.out.println(f.setReadOnly());
        System.out.println(f.canWrite());
    }
}

11.在指定目录中创建文件

public class MainClass{
    public static void main(String[] args) throws Exception{
        File dir = new File("c:/");
        File f = File.createTempFile("test", ".txt", dir);
        System.out.println(f.getPath());
    }
}

12.文件路径比较

public class MainClass{
    public static void main(String[] args) throws Exception{
        File dir1 = new File("c:/temp/test.txt");
        File dir2 = new File("C:/java/test.txt");
        if(dir1.compareTo(dir2)==0){
            System.out.println("路径一致");
        }else{
            System.out.println("不一致");
        }
    }
}