Java 学习之IO类基础（一）

布满荆棘的人生 2022-06-12 06:46 221阅读 0赞

今天整理了一下java中IO类中的一些基本的知识点和一些类和方法的使用。

其中也借鉴了别人的博客： http://blog.csdn.net/pistolove/article/details/62210164

Java中IO操作通常指的是使用java 对数据进行读写操作，机制就是通过数据流进行读写。

何谓数据流呢，数据流就是表示字节或者字符的流动序列

简而言之：数据流就是包括输入流和输出流的有序的有起点和有终点 的字节的数据序列

当程序需要读取数据时就要创建一个通向数据源的连接，这个数据源可以是 文件，也可以是内存，也可以是网络连接，当程序需要写入数据的，也需要创建一个通向目的地i的连接。

流序列中的数据既可以是未经加工的原始二进制数据，也可以是经过一定编码的符合某种格式的特定数据，Java中的流分为两种

1.字节流： 数据流中最小的数据单元是字节

2.字符流： 数据流中最小的数据单元是字符， java中的字符是Unicode编码，一个字符占用连个字节

基于字节的输入输出流

比较常用的字节的输入流有：

1. FileInputStream(文件输入流)

2. ByteArrayInputStream (字节数组输入流)

3. BufferedInputStream (缓冲输入流)

以上三个字节输入流都是继承自 InputStream

下面是字节流的练习

public static void test01(){
    		String rootPath = System.getProperty("user.dir");
    		File file1 = new File(rootPath+File.separator+"template"+File.separator+"json"+File.separator+"1.json");
    		File file2 = new File(rootPath+File.separator+"template"+File.separator+"json"+File.separator+"2.json");
    		FileInputStream in = null;
    		FileOutputStream out = null;
    		try {
    			in = new FileInputStream(file1);
    			boolean flag = file2.exists();
    			out = new FileOutputStream(file2);
    			byte[] buff = new byte[2048];
    			while(in.read(buff)!=-1){
    				out.write(buff);
    			}
    			System.out.println("写入完毕");
    			in.close();
    			out.close();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			if(in!=null){
    				try {
    					in.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    			if(out!=null){
    				try {
    					out.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    		}
    	}

public static void test02(){
    		ByteArrayInputStream in = null;
    		ByteArrayOutputStream out = null;
    		String str = "我爱你 nsi";
    		byte[] buff = new byte[20480];
    		try {
    			in = new ByteArrayInputStream(str.getBytes());
    			out = new ByteArrayOutputStream();
    			while(in.read(buff)!=-1){
    				out.write(buff);
    			}
    			System.out.println("写入完毕了");
    			System.out.println(out.toString());
    			in.close();
    			out.close();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			if(in!=null){
    				try {
    					in.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    			if(out!=null){
    				try {
    					out.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    		}
    	}

public static void test03(){
    		String rootPath = System.getProperty("user.dir");
    		File file1 = new File(rootPath+File.separator+"template"+File.separator+"json"+File.separator+"1.json");
    		File file2 = new File(rootPath+File.separator+"template"+File.separator+"json"+File.separator+"2.json");
    		BufferedInputStream in = null;
    		BufferedOutputStream out = null;
    		try {
    			in = new BufferedInputStream(new FileInputStream(file1));
    			out = new BufferedOutputStream(new FileOutputStream(file2));
    			byte[] buff = new byte[1024];
    			while(in.read(buff)!=-1){
    				out.write(buff);
    			}
    			System.out.println("写入完毕");
    			in.close();
    			out.close();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			if(in!=null){
    				try {
    					in.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    			if(out!=null){
    				try {
    					out.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    		}
    	}

下面是字符流的练习

/\*\*  
\* 基于字符的输入输出流  
\* 输入流：   
\* 1. FileReader  
\* 2. InputStreamReader  
\* 3. StringReader  
\* 输出流  
\* 1. FileWriter  
\* 2. OutputStreamWriter  
\* 3. StringWriter  
\*/

public static void test04(){
    		String rootPath = System.getProperty("user.dir");
    		File file1 = new File(rootPath+File.separator+"template"+File.separator+"json"+File.separator+"1.json");
    		File file2 = new File(rootPath+File.separator+"template"+File.separator+"json"+File.separator+"2.json");
    		FileReader reader = null;
    		FileWriter writer = null;
    		char[] chaff = new char[2048];
    		try {
    			reader = new FileReader(file1);
    			writer = new FileWriter(file2);
    			while(reader.read(chaff)!=-1){
    				writer.write(chaff);
    			}
    			System.out.println("写入完毕");
    			reader.close();
    			writer.close();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			if(reader!=null){
    				try {
    					reader.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    			if(writer!=null){
    				try {
    					writer.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    		}
    	}

public static void test05(){
    		String rootPath = System.getProperty("user.dir");
    		File file1 = new File(rootPath+File.separator+"template"+File.separator+"json"+File.separator+"1.json");
    		File file2 = new File(rootPath+File.separator+"template"+File.separator+"json"+File.separator+"3.json");
    		InputStreamReader isr = null;
    		OutputStreamWriter osw = null;
    		char[] chaff = new char[2048];
    		try {
    			//多种实现
    //			isr = new InputStreamReader(new FileInputStream(file1));
    //			isr = new InputStreamReader(new BufferedInputStream(new FileInputStream(file1)));
    			isr = new InputStreamReader(new ByteArrayInputStream(new String("三块经销商njkk214  &&%%NJKBAS  寸你看电视剧").getBytes()));
    			
    //			osw = new OutputStreamWriter(new FileOutputStream(file2));
    			osw = new OutputStreamWriter(new BufferedOutputStream(new FileOutputStream(file2)));
    //			osw = new OutputStreamWriter(new ByteArrayOutputStream());
    
    			if(isr.read(chaff)!=-1){
    				osw.write(chaff);
    			}
    			System.out.println("写入成功");
    			osw.flush();
    			System.out.println(osw.toString());
    			isr.close();
    			osw.close();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			if(isr!=null){
    				try {
    					isr.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    			if(osw!=null){
    				try {
    					osw.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    		}
    	}

public static void test06(){
    		StringReader reader = null;
    		StringWriter writer = null;
    		try {
    			reader = new StringReader("我爱你中华 Ilove you !!!");
    			writer = new StringWriter();
    			char[] chaff = new char[2048];
    			if(reader.read(chaff)!=-1){
    				writer.write(chaff);
    			}
    			System.out.println("写入完毕");
    			System.out.println(writer.toString());
    			reader.close();
    			writer.close();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			if(reader!=null){
    				reader.close();
    			}
    			if(writer!=null){
    				try {
    					writer.close();
    				} catch (IOException e) {
    					e.printStackTrace();
    				}
    			}
    		}
    	}

总的来说学习IO类，就要学习，InputStream,OutputStream, Reader, Writer 这几个抽象类，以及继承他们的类

输入流和输出流都要注意创建一个有起始端和 终点端的连接

不积跬步，无以至千里

不积小流，无以成江海