File类

1 凡是输入、输出的类，接口都在java.io下

2 File是一个类，可由构造器创建其对象。此对象对应一个文件或目录。分为：绝对路径和相对路径

3 File类对象与平台无关的

4 File中的方法，仅涉及到如何创建、删除、重命名等等。只要涉及文件内容，File方法无能为力，只能用io流决定

5 File类的对象常作为io留的具体类的构造器的形参

package lianxi1;

import java.io.File;
import java.io.IOException;
import java.util.Date;

import org.junit.Test;

public class TestFile {
@Test //访问文件
   public void Test1(){
    //File对象对应一个文件或目录,分为绝对路径和相对路径
    File file1 = new File("d:/io/helloworld.txt"); //或者（“d:\\io\\helloworld.txt")
    File file2 = new File("d:\\io\\io1");
    File file3 = new File("Goodbye2");
    
    System.out.println(file1.getName());
    System.out.println(file1.getPath());
    System.out.println(file1.getAbsolutePath());
    System.out.println(file1.getParent());
    System.out.println(file1.getAbsoluteFile());
    
    System.out.println(file3.getName());
    System.out.println(file3.getPath());
    System.out.println(file3.getAbsolutePath());
    System.out.println(file3.getParent());
    System.out.println(file3.getAbsoluteFile());
    //file1.renameTo(file2)要求file1一定存在，file2一定不存在
    boolean t = file1.renameTo(file3);
    System.out.println(t);
}
@Test //文件检测
public void Test2(){
    File file2 = new File("d:\\io\\io1");
    System.out.println(file2.exists());
    System.out.println(file2.canRead());
    System.out.println(file2.canWrite());
    System.out.println(file2.canExecute());
    System.out.println(file2.isDirectory());
    System.out.println(new Date(file2.lastModified()));
    System.out.println(file2.length());
}
@Test //文件和目录操作
public void Test3() throws IOException{
    File file1 = new File("d:/io/helloworld.txt");  
    System.out.println(file1.delete());            //true
    if(!file1.exists()){
        System.out.println(file1.createNewFile()); //true
    }
    File file2 = new File("d:\\io3\\io2");
    if(!file2.exists()){
        System.out.println(file2.mkdir());   //false
        System.out.println(file2.mkdirs());  //true
    }
    File file3 = new File("d:\\");
    String[] strs = file3.list();
    for(String s1:strs){
        System.out.println(s1);
    }
    System.out.println();
    File file4 = new File("d:\\");
    File[] strs2 = file3.listFiles();
    for(File s2:strs2){
        System.out.println(new Date(s2.lastModified()));
    }
    
}
}