Java学习 之 IO流

1.实现FilenameFilter接口，应用accept方法实现遍历指定目录下的所有符合条件的文件，这里以遍历出所有的.java文件为例：

 

 

import java.io.File;
import java.io.FilenameFilter;

public class File_list_accept {
	/**
	 * Main 方法，程序入口
	 * @param args
	 */
	public static void main(String[] args) {
		File file = new File(".");
		File[] nameList = file.listFiles(new MyFilenameFilter());		
		for (File name : nameList) {
			if (name.getAbsoluteFile().isDirectory()) {
				File[] nameListFiles = name.listFiles(new MyFilenameFilter());
				for (File name1 : nameListFiles) {
					System.out.println(name1.getName());
				}
			}
		}
	}

}

class MyFilenameFilter implements FilenameFilter {

	@Override
	public boolean accept(File dir, String name) {
		return name.endsWith(".java")||new File(name).isDirectory();
	}

}

 

 

2.PrintStream类的练习

 

import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintStream;

public class PrintStreamText {
	public static void main(String[] args) throws FileNotFoundException {
		PrintStream printStream = null;
		FileOutputStream fos = new FileOutputStream("printStream.txt");
		printStream = new PrintStream(fos);
		printStream.println("Java 处理流体系之PrintStream流的测试代码");
		printStream.print(new PrintStreamText());
		printStream.close();
		// 这里我们只需要关闭处理流PrintStream即可，而不必关心FileOutputSream
		// 因为当我们关闭了最上层的处理流时，系统会自动关闭被该处理流包装的节点流
	}
}

 

 

 

3.输入流FileInputStream和FileReader

 

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;


public class Read_FileInputStream_and_FileReader {
	
	public static void main(String[] args) {
		Read_FileInputStream_and_FileReader file = new Read_FileInputStream_and_FileReader();
//		file.fileInputSreamMethod();
		file.fileReaderMethod();
	}
	
	/**
	 *  使用字节流读取数据
	 */
	public void fileInputSreamMethod(){
		FileInputStream fileInputStream = null;
		try {
			// 中文注释
//			fileInputStream = new FileInputStream("D:\\D\\Android_Code\\Java_IO_(1)\\src\\File.java");
			fileInputStream = new FileInputStream("./src/File_list_accept.java");
			byte[] bytes = new byte[1024];// 当这里的数组设置成1时，输出上面的“中文注释”时将出现乱码，
			// 这是因为每个中文字符占据2个字节，而read方法读取时只读到了半个中文字符，因此导致乱码
			int readCount  = 0;
			while ((readCount  = fileInputStream.read(bytes)) > 0) {
				System.out.println(new String(bytes, 0, readCount));
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
				if (fileInputStream != null) {
					try {
						fileInputStream.close();
					} catch (IOException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
		}
	}
	
	/**
	 * 使用字符流读取数据
	 */
	public void fileReaderMethod(){
		FileReader fileReader = null;
		try {
			fileReader = new FileReader("./src/File_list_accept.java");
//			fileReader.skip(200);
			char[] chars = new char[1024];
			int readCount = 0;
			while ((readCount = fileReader.read(chars)) > 0) {
				System.out.println(new String(chars, 0, readCount));
			}
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			if (fileReader != null) {
				try {
					fileReader.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		
	}
	
}

 

 

 

4.输出流FileOutputStream和FileWriter

 

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;


public class Write_FileOutputStream_and_FileWriter {
	public static void main(String[] args) throws IOException {
		/**
		 * FileInputStream
		 */
		FileInputStream fileInputStream = null;
		FileOutputStream fileOutputStream = null;
		fileInputStream = new FileInputStream("./src/File_list_accept.java");
		fileOutputStream = new FileOutputStream("newFile.txt");
		byte[] bytes = new byte[1024];
		int readCount = 0;
		while ((readCount = fileInputStream.read(bytes)) > 0) {
			fileOutputStream.write(bytes, 0, readCount);
		}
		if (fileInputStream != null) {
			fileInputStream.close();
		}
		if (fileOutputStream != null) {
			fileOutputStream.close();
		}
		
		/**
		 * FileWriter
		 */
		FileWriter fileWriter = null;
		fileWriter = new FileWriter("./fileWriter.txt");
		fileWriter.write("---------黄鹤楼---------\r\n"); 
		// \r\n是Window的换行符，Linux等则用\n即可
		fileWriter.write("白日依山尽，黄河入海流。\r\n");
		fileWriter.write("欲穷千里目，更上一层楼。");
		if (fileWriter != null) {
			fileWriter.close();
		}
	}
}