毕向东_Java基础视频教程第20天_IO流（15~17）

第20天-15-IO流(打印输出流)

打印输出流：PrintWriter与PrintStream

两者的区别：Since JDK 1.4 it's possible to specify the character encoding for a PrintStream. Thus, the differences between PrintStream and PrintWriter are only about auto flushing behavior and that a PrintStream cannot wrap a Writer.

package bxd;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;

/*
打印输出流: 该流提供了打印方法, 可以将各种类型的数据都原样打印

PrintStream构造函数可以接受的参数类型:
1. File对象 File
2. 字符串路径 String
3. 字节输出流 OutputStream

PrintWriter构造函数可以接受的参数类型(由于可接受的参数类型更多, 因而更常用一些):
1. File对象 File
2. 字符串路径 String
3. 字节输出流 OutputStream
4. 字符输出流 Writer
*/
public class PrintStreamDemo {
    public static void main(String[] args) throws IOException {

        BufferedReader bufr = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter out = new PrintWriter(System.out, true);

        String line = null;
        while ((line = bufr.readLine()) != null) {
            if ("over".equals(line)) break;
            out.println(line.toUpperCase());
        }
        out.close();
        bufr.close();
    }
}

第20天-16-IO流(合并流-SequenceInputStream)

package bxd;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.SequenceInputStream;
import java.util.Enumeration;
import java.util.Vector;

public class SequenceDemo {

    public static void main(String[] args) throws IOException {

        Vector<FileInputStream> v = new Vector<FileInputStream>();
        v.add(new FileInputStream("info.txt"));
        v.add(new FileInputStream("list.txt"));
        Enumeration<FileInputStream> en = v.elements();

        SequenceInputStream sis = new SequenceInputStream(en);
        FileOutputStream fos = new FileOutputStream("uni.txt");

        byte[] buf = new byte[1024];
        int len = 0;
        while ((len = sis.read(buf)) != -1) {
            fos.write(buf, 0, len);
        }

        fos.close();
        sis.close();
    }
}

第20天-17-IO流(切割文件)

package bxd;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.SequenceInputStream;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;

public class SplitFile {
    public static void splitFile() throws IOException {
        FileInputStream fis = new FileInputStream("ts.png");
        FileOutputStream fos = null;

        byte[] bytes = new byte[600 * 1024];
        int len = 0;
        int count = 1;
        while ((len = fis.read(bytes)) != -1) {
            fos = new FileOutputStream((count++) + ".part");
            fos.write(bytes, 0, len);
            fos.close();
        }
        fis.close();
    }

    public static void merge() throws IOException {

        ArrayList<FileInputStream> al = new ArrayList<FileInputStream>();
        for (int x = 1; x <= 4; x++) al.add(new FileInputStream(x + ".part"));

        final Iterator<FileInputStream> it = al.iterator();
        Enumeration<FileInputStream> en = new Enumeration<FileInputStream>() {
            @Override
            public boolean hasMoreElements() {
                return it.hasNext();
            }

            @Override
            public FileInputStream nextElement() {
                return it.next();
            }
        };

        SequenceInputStream sis = new SequenceInputStream(en);
        FileOutputStream fos = new FileOutputStream("rets.png");

        byte[] bytes = new byte[1024];
        int len = 0;
        while ((len = sis.read(bytes)) != -1) fos.write(bytes, 0, len);

        fos.close();
        sis.close();
    }

    public static void main(String[] args) throws IOException {
        merge();
    }
}