java常用类解析三：IO系统装饰类

java IO系统采用装饰器模式，用一些装饰类来装饰输入输出来，提供更强大的IO操作

FilterInputStream(FilterOutputStream)继承自InputStream(Outputstream)

常用装饰类(都继承自FilterInputStream)               功能

DataInputStream(DataOutputStream)                 读写基本类型即UTF

BufferedInputStream(BufferedOutputStream)      使用缓冲区

PrintStream继承自Outputstream，用于格式化输出到文本或控制台等

 

 

示例：

<span style="font-size:16px;">package test;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

/*
 * DataInputStream继承自FilterInputStream(FilterInputStream继承自InputStream)
 * 用来装饰InputStream，提供可移植方式从流读取基本数据类型
 * DataOutputStream继承自FilterOutputStream(FilterOutputStream继承自OutputStream)
 * 用来装饰OutputStream，提供可移植方式向流写入基本数据类型
 * DataInputStream/DataOutputStream可以实现数据的存储与恢复
 */
public class DataInputStreamDemo {
    public static void main(String[] args) {
        DataOutputStream dataOutStream = null;
        try {
            dataOutStream = new DataOutputStream(new BufferedOutputStream(
                    new FileOutputStream("file/aa.data")));
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        try {// 写入文件
            dataOutStream.writeChar('a');
            dataOutStream.writeInt(3);
            dataOutStream.writeDouble(5.5);
            dataOutStream.writeFloat(3.2f);
            dataOutStream.writeUTF("nihaoma");
            dataOutStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }

        DataInputStream dataInputStream = null;
        try {
            dataInputStream = new DataInputStream(new BufferedInputStream(
                    new FileInputStream("file/aa.data")));
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        try {// 读取文件
            System.out.println(dataInputStream.readChar());
            System.out.println(dataInputStream.readInt());
            System.out.println(dataInputStream.readDouble());
            System.out.println(dataInputStream.readFloat());
            System.out.println(dataInputStream.readUTF());
            dataInputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
</span>

 

<span style="font-size:16px;">package test;

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

/*
 * 继承自FilterOutputStream，其中DataOutputStream处理数据的存储，PrintStream处理显示
 * 用于格式化打印
 */
public class PrintStreamDemo {
    public static void main(String[] args) throws FileNotFoundException {
        // 把数据可视化格式显示到文本文件中
        PrintStream printStream = new PrintStream("file/test2.txt");
        printStream.println('a');
        printStream.println(2);
        printStream.println(3.2);
        printStream.println("liuhaifang");
        printStream.println("刘海房");
        // 可视化显示到控制台
        printStream = new PrintStream(System.out);
        printStream.println("hello  java");
    }
}
</span>