文件操作File

青旅半醒 2022-07-25 16:45 193阅读 0赞

***纸上得来终觉浅***

**1.java文件和文件夹的操作**

public class abs{
    	public static void main(String[] args) {
    /*文件操作*/		
    		File myFile = new File("test.txt");
    		if(!myFile.exists()){
    			System.out.println("myfile:文件不存在");
    			try {
    				myFile.createNewFile();
    			} catch (IOException e) {
    				e.printStackTrace();
    			}
    			System.out.println("myfile创建成功");
    		}else{
    			System.out.println("myfile已经存在");
    		}
    		System.out.println("绝对路径："+myFile.getAbsolutePath());
    		System.out.println("父级目录:"+new File(myFile.getAbsolutePath()).getParent());
    		System.out.println("相对路径："+myFile.getPath());
    		System.out.println("文件名："+myFile.getName());
    		System.out.println("是否文件夹："+myFile.isDirectory());
    		System.out.println("是否文件："+myFile.isFile());
    		
    		System.out.println("是否可读："+myFile.canRead());
    		System.out.println("是否可写："+myFile.canWrite());
    		System.out.println();
    		
    		/*在windows在文件可读性不能被设置为false，所以这里的设置失效，如果生效的话可读为false，可写为false*/
    		System.out.println("设置不可读"+myFile.setReadable(false));
    		System.out.println("是否可读："+myFile.canRead());
    		System.out.println("是否可写："+myFile.canWrite());
    		System.out.println();
    		
    		System.out.println("设置可读"+myFile.setReadable(true));
    		System.out.println("设置不可写"+myFile.setWritable(false));
    		System.out.println("是否可读："+myFile.canRead());
    		System.out.println("是否可写："+myFile.canWrite());
    		System.out.println();
    		
    		System.out.println("设置不可读"+myFile.setReadable(false));
    		System.out.println("设置可写"+myFile.setWritable(true));
    		System.out.println("是否可读："+myFile.canRead());
    		System.out.println("是否可写："+myFile.canWrite());
    		System.out.println();
    		
    		System.out.println("设置只可读"+myFile.setReadOnly());
    		System.out.println("是否可读："+myFile.canRead());
    		System.out.println("是否可写："+myFile.canWrite());
    		System.out.println();
    		
    		System.out.println("文件长度："+myFile.length());
    		System.out.println("文件是否隐藏："+myFile.isHidden());
    		
    		
    		System.out.println("输出数据前设置可写"+myFile.setWritable(true));
    		/*输出数据到文件*/
    		try {
    			FileOutputStream fileOutputStream = new FileOutputStream(myFile);
    			OutputStreamWriter outputStreamWriter = new OutputStreamWriter(fileOutputStream,"UTF-8");
    			BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter);
    			bufferedWriter.write("白日依山尽\n");
    			bufferedWriter.write("黄河入海流\n");
    			bufferedWriter.write("欲穷千里目\n");
    			bufferedWriter.write("更上一层楼\n");
    			bufferedWriter.close();
    			outputStreamWriter.close();
    			fileOutputStream.close();
    		} catch (FileNotFoundException e1) {
    			e1.printStackTrace();
    		} catch (IOException e1) {
    			e1.printStackTrace();
    		}
    		System.out.println("文件长度："+myFile.length());
    		System.out.println();
    		
    		try {
    			FileInputStream fileInputStream = new FileInputStream(myFile);
    			InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream,"UTF-8");
    			BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
    			String line;
    			while((line = bufferedReader.readLine())!=null){
    				System.out.println(line);
    			}
    			bufferedReader.close();
    			inputStreamReader.close();
    			fileInputStream.close();
    		} catch (FileNotFoundException e) {
    			e.printStackTrace();
    		} catch (IOException e) {
    			e.printStackTrace();
    		}
    		
    		File myfile2 = new File("test2.txt");
    		myFile.renameTo(myfile2);
    		
    		if(myFile.delete()){
    			System.out.println("旧文件删除成功");
    		}else{
    			System.out.println("旧文件删除失败");
    			if(myfile2.exists()){
    				myfile2.delete();
    				System.out.println("新文件删除成功");
    			}else{
    				System.out.println("新文件删除失败");
    			}
    		}
    		
    /*文件夹操作*/
    		File myFoder = new File("test");
    		if(!myFoder.exists()){
    			System.out.println("myFoder:文件夹不存在");
    			myFoder.mkdirs();
    		}else{
    			System.out.println("文件夹已经存在");
    		}
    		
    		File myfoder2 = new File("test2");
    		myFoder.renameTo(myfoder2);
    		
    		if(myFoder.delete()){
    			System.out.println("旧文件夹删除成功");
    		}else{
    			System.out.println("旧文件夹删除失败");
    			if(myfoder2.exists()){
    				myfoder2.delete();
    				System.out.println("新文件夹删除成功");
    			}else{
    				System.out.println("新文件夹删除失败");
    			}
    		}
    		
    		//文件夹内部文件遍历
    		File myFoder3 = new File("src");
    		if(!myFoder3.exists()){
    			System.out.println("src文件夹不存在");
    		}else{
    			search(myFoder3,1);
    		}
    	}
    	
    	public static void search(File file,int i){
    		String tab = "";
    		int i2 = i;
    		while(i2-->0){tab+="-";}
    		System.out.println(tab+file.getName());
    		if(!file.isFile()){
    			File newFile[] = file.listFiles();
    			i++;
    			for (int x = 0; x < newFile.length; x++) {
    				search(newFile[x],i);
    			}
    		}
    	}
    }

下面是运行结果：

![Center][]

![Center 1][]

**2.注意一下几点：**

1) windows不可设置文件属性为不可读，所以上段代码设置不可读是失效。

2)windows  rename操作必须在同一个分区中。

3)设置属性之间的关系：

A: 如果设置了可写，一定是可读可写的。

B:如果设置了可读为真，可以是不可写的。

C:如果设置了可读为假，一定是不可读不可写的。

以上三点基于这样的命题即可：可读是可写必要条件

D：setReadable(true) +setWritable(false)等同于 setReadOnly