java--標准輸入輸出流

//讀取鍵盤錄入的數據寫到a.txt
//方式一
private static void method() throws IOException {
	//創建輸入流對象
	InputStream is = System.in;
	Reader r = new InputStreamReader(is);
	//創建輸出流對象
	FileWriter fw = new FileWriter("a.txt");
	
	//讀取數據
	byte[] bys = new byte[1024];
	int len;
	while((len = is.read(bys))!=-1)
	{
		fw.write(new String(bys, 0, len));
		fw.flush();
	}
	fw.close();
	is.close();
}

//方式二
private static void method2() throws IOException {
	//創建輸入流對象
	InputStream is = System.in;
	Reader r = new InputStreamReader(is);
	//創建輸出流對象
	FileWriter fw = new FileWriter("a.txt");
	
	//讀取數據
	char[] chs = new char[1024];
	int len;
	while((len = r.read(chs))!=-1)
	{
		fw.write(chs, 0 , len);
		fw.flush();
	}
	fw.close();
	r.close();
}


// 將文件中的數據輸出到控制台
	BufferedReader br = new BufferedReader(new FileReader("a.txt"));
	
	//OutputStream os = System.out;
	//Writer w = new OutputStreamWriter(System.out);
	//BufferedWriter bw = new BufferedWriter(w);
	BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
	
	String line;
	while((line = br.readLine())!=null)
	{
		bw.write(line);
		bw.newLine();
	}
	bw.close();
	br.close();

//使用打印流復制文本文件
private static void method3() throws FileNotFoundException, IOException {
	//創建輸入流對象
	BufferedReader br = new BufferedReader(new FileReader("a.txt"));
	//創建打印流對象
	PrintWriter pw = new PrintWriter(new FileWriter("b.txt"),true);  // 此處true，是自動刷新
	String line;
	while((line = br.readLine())!=null)
	{
		pw.println(line);
	}
	pw.close();
	br.close();
	}


//使用字節流進行文件的復制（復制二進制文件）

private static void method() throws FileNotFoundException, IOException {
	FileInputStream fis = new FileInputStream("這里是一個文件名");
	FileOutputStream fos = new FileOutputStream("另一個問件名");
	
// 一次讀一個字節
//		int by;
//		while((by = fis.read() ) !=-1){
//			fos.write(by);
//		}
	
	// 一次讀取一個字符數組
	int len;
	byte[] bys = new byte[1024];
	while((len = fis.read(bys))!=1){
		fos.write(len);
	}
	
	fis.close();
	fos.close();
}

對象操作流

可以用於讀寫任意類型的對象
ObjectOutputStream :對象輸出字符流
WriteObject
ObjectInputStream ：對象輸入字符流
ReadObject
注意：
使用對象輸出流寫出對象，只能使用對象輸入流來讀取對象
只能將支持java.io.Serializable 接口的對象寫入流中
Serializable：序列號，是一個標識接口，只起表示作用，沒有方法
當一個類的對象需要進行IO流進行讀寫的時候，這個類必須實現此接口

//eg:創建用於文件讀寫的學生類對象
public class Student implements Serializable{
	private static final long serialVersionUID = -4114259825335049236L;	 // 固定序列號
	String name;
	int age;
	
	public Student(String name,int age) {
		this.age = age;
		this.name = name;
	}
	@Override
	public String toString() {
		return "Student [name=" + name + ", age=" + age + "]";
	}
	
}




//將學生對象寫入文件
private static void method() throws IOException, FileNotFoundException {
	//創建對象輸出流的對象
	//FileOutputStream fos = new FileOutputStream("a.txt"); // 字節輸出流
	//ObjectOutputStream oos = new ObjectOutputStream(fos);
	ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("a.txt"));
	
	//創建學生對象
	Student s = new Student("zhangsan", 18);
	Student s2 = new Student("lisi",19);
	
	//寫出學生對象
	oos.writeObject(s);
	oos.writeObject(s2);
	
	//釋放資源
	oos.close();
}



//將文件中的學生對象讀取出來
	private static void method2() throws IOException, FileNotFoundException, ClassNotFoundException {
		//創建對象輸入流的對象
		ObjectInputStream ois = new ObjectInputStream(new FileInputStream("a.txt"));
	/*	//讀取對象	
		java.lang.Object obj = ois.readObject();
		System.out.println(obj);
		
		java.lang.Object obj2 = ois.readObject();
		System.out.println(obj2);
		
		java.lang.Object obj3 = ois.readObject();
		System.out.println(obj3);*/
		
		try{
			while(true)
			{
				java.lang.Object obj = ois.readObject();
				System.out.println(obj);
			}
		} catch(EOFException e){
			System.out.println("讀到了文件的末尾");
		}
		//釋放資源
		ois.close();
	}




// 另一種方式寫入
private static void method3() throws IOException, FileNotFoundException {
	// 另一種寫入對象文件的方式（將所有對象寫入到集合對象中）
	//創建對象輸出流對象
	ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("b.txt"));
	//創建集合對象
	ArrayList<Student> list = new ArrayList<Student>();
	//添加學生對象
	list.add(new Student("wangwu", 19));
	list.add(new Student("zhaoliu", 20));
	//寫出集合對象
	oos.writeObject(list);
	
	//釋放資源
	oos.close();
}


//另一種讀取方式
private static void method4() throws IOException, FileNotFoundException, ClassNotFoundException {
	//創建對象輸出流對象
	ObjectInputStream ois = new ObjectInputStream(new FileInputStream("b.txt"));
	//讀取數據
	java.lang.Object obj = ois.readObject();
	//System.out.println(obj);
	// 向下轉型，獲取具體的子類對象
	ArrayList<Student> list = (ArrayList<Student>) obj;
	for(Student stu:list)
	{
		System.out.println(stu);
	}
	
	//釋放資源
	ois.close();
}