File类

概述

File文件和路径名的抽象表示形式

graph TD A[File] B[路径] A --> C[相对路径] A --> D[绝对路径]

构造方法

File(String pathname) 根据一个路径得到File对象
FIle(String parent, String child) 根据一个目录和一个子文件/目录得到一个File对象
File(FIle parent, String child) 根据一个父File对象和一个子文件/目录得到File对象
File(URI uri) 通过将给定的file:URI转化为抽象路径名来创建新的File对象

import java.io.File;

public class DemoFile {

	public static void main(String[] args) {
		File file = new File("/home/mephisto/eclipse-workspace/learnjava/src/com/mephisto/file/demo.txt");
		System.out.println(file.exists());
		
		File file2 = new File("/home/mephisto/eclipse-workspace/learnjava/src/com/mephisto/file/","demo.txt");
		System.out.println(file2.exists());
		
		
		File parent = new File("/home/mephisto/eclipse-workspace/learnjava/src/com/mephisto/file/");
		String child = "demo.txt";
		System.out.println(new File(parent,child).exists());
	}

}

创建功能

public boolean createNewFile(): 创建文件如果存在这样的文件就不创建
public boolean mkdir() : 创建文件夹, 如果存在这样的文件夹, 就不创建
public boolean madirs(): 创建文件夹, 如果父文件夹不存在,会创建出来, 类似递归创建

import java.io.File;
import java.io.IOException;

public class DemoFildMethod {
	public static void main(String[] args) throws IOException {
		String pathname = "/home/mephisto/eclipse-workspace/learnjava/src/com/mephisto/file";
		File file = new File(pathname + "test");
		file.createNewFile();
		
		File file2 = new File(pathname + "demo");
		file2.mkdir();
		
		
		File file3 = new File(pathname + "demotest/test");
		file3.mkdirs();
	}

}

重命名和删除功能

方法

public boolean rename(File dest) 把文件重命名为指定的文件路径
public boolean delete() 删除文件或文件夹

重命名注意事项

如果路径名相同, 就是改名
如果路径名不同, 就是改名并剪切

删除注意事项

Java中的删除不走回收站
要删除一个文件夹, 注意该文件夹下不能包含文件或者文件夹

import java.io.File;

public class DemoDeleteOrRename {

	public static void main(String[] args) {
		String pathname = "/home/mephisto/eclipse-workspace/learnjava/src/com/mephisto/file";
		File file = new File(pathname,"test");
		file.delete();
		
		File file3 = new File(pathname,"demotest");
		System.out.println(file3.delete());  // false
		
		
		File file2 = new File(pathname,"demo.txt");
		file2.renameTo(new File(pathname,"Demo"));
	}
}

判断功能

方法

public boolean isDirectory() : 判断是否是目录
public boolean isFile() : 判断是否是文件
public boolean exists() : 判断是否存在
public boolean canRead() : 判断是否可读
public boolean canWrite() : 判断是否可写
public boolean isHidden() : 判断是否隐藏

import java.io.File;

public class DemoJudge {

	public static void main(String[] args) {
		String pathname = "/home/mephisto/eclipse-workspace/learnjava/src/com/mephisto/file";
		
		File file = new File(pathname);
		System.out.println(file.isDirectory());
		
		File file2 = new File(pathname,"Demo");
		System.out.println(file2.canRead());
		System.out.println(file2.canWrite());
		
		
		// windows系统认为所有文件都是可读的, 不可以设置是否可读, 可以设置是否可写
		file2.setReadable(false);
		System.out.println(file2.canRead());
		file2.setWritable(false);
		System.out.println(file2.canWrite());
		file2.setReadable(true);
		file2.setWritable(true);
		
		file2.renameTo(new File(pathname,".Demo"));
		File file3 = new File(pathname,".Demo");
		System.out.println(file3.isHidden());
		
		File file4 = new File(pathname,".Demo");
		file4.renameTo(new File(pathname,"Demo"));
	}
}

获取功能

方法

public String getAbsolutePath() 获取绝对路径
public String getPath() 获取路径
public String getName() 获取名称
public long lenth() 获取字节数
pubic long lastModified() 获取最后一次修改的时间,毫秒值
public String[] list() 获取指定目录下的所有文件或者文件夹的名称数组
public File[] listFiles() 获取指定目录下的所有文件或者文件夹的File数组

import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;

public class DemoGetMethod {
	public static void main(String[] args) {
		String pathname = "/home/mephisto/eclipse-workspace/learnjava/src/com/mephisto/file";
		File file = new File(pathname, "Demo");

		System.out.println(file.getPath());

		System.out.println(file.getName());

		System.out.println(file.getAbsolutePath());

		System.out.println(file.length());

		System.out.println(new SimpleDateFormat("yyyy年MM月dd日HH:mm:ss").format(new Date(file.lastModified())));

		String dirName = "/home/mephisto/eclipse-workspace/learnjava/src/com/mephisto/file";
		File file2 = new File(dirName);
		for (String string : file2.list()) {
			System.out.println(string);
		}

		System.out.println("===============");

		for (File file3 : file2.listFiles()) {
			System.out.println(file3.getName());
		}
	}
}

文件名称过滤器

方法

public String[] list(FilenameFilter filter)
public File[] listFiles(FileFilter filter)