JAVA之旅（三十）——打印流PrintWriter，合并流，切割文件并且合并，对象的序列化Serializable，管道流，RandomAccessFile，IO其他类，字符编码

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一.打印流PrintWriter

• 该流提供了打印方法，可以将各种数据类型原样打印
  • file对象 File
  • 字符串路径 String
  • 字节打印流
  • 字符打印流

package com.lgl.hellojava;

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

public class HelloJJAVA {
    public static void main(String[] args) {

        try {
            BufferedReader bufr = new BufferedReader(new InputStreamReader(
                    System.in));

            PrintWriter oWriter = new PrintWriter(System.out, true);
            String line = null;
            while ((line = bufr.readLine()) != null) {
                if (line.equals("over")) {
                    break;
                }
                oWriter.write(line);
            }
            oWriter.close();
            bufr.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

二.合并流

package com.lgl.hellojava;

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

public class HelloJJAVA {
    public static void main(String[] args) {
        try {
            Vector<FileInputStream> v = new Vector<FileInputStream>();
            v.add(new FileInputStream("1.txt"));
            v.add(new FileInputStream("2.txt"));
            Enumeration<FileInputStream> elements = v.elements();
            SequenceInputStream sis = new SequenceInputStream(elements);

            FileOutputStream fos = new FileOutputStream("3.txt");

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

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

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

三.切割文件

// 切割文件
    public static void splitFile() {
        try {
            FileInputStream fis = new FileInputStream("1.jpg");
            FileOutputStream fos = null;
            byte[] buf = new byte[1024 * 1024];

            int len = 0;
            int count = 1;
            while ((len = fis.read(buf)) != -1) {
                fos = new FileOutputStream((count++) + ".patch");
                fos.write(buf, 0, len);
                fos.close();
            }

            fis.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

// 合并文件
    public static void merge() {
        ArrayList<FileInputStream> al = new ArrayList<>();
        for (int i = 1; i <= 2; i++) {
            try {
                al.add(new FileInputStream(i + ".patch"));
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        Iterator<FileInputStream> iterator = al.iterator();
        Enumeration<FileInputStream> en = new Enumeration<FileInputStream>() {

            @Override
            public boolean hasMoreElements() {
                // TODO Auto-generated method stub
                return iterator.hasNext();
            }

            @Override
            public FileInputStream nextElement() {
                // TODO Auto-generated method stub
                return iterator.next();
            }

        };
        try {
            SequenceInputStream seq = new SequenceInputStream(en);
            FileOutputStream fos = new FileOutputStream("2.jpg");

            byte[] buf = new byte[1024];

            int len = 0;

            while ((len = seq.read(buf)) != -1) {
                fos.write(buf, 0, len);
            }

            fos.close();
            seq.close();

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

四.对象的序列化Serializable

package com.lgl.hellojava;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class HelloJJAVA {
    public static void main(String[] args) {
        // writeObj();
        readObj();
    }

    private static void readObj() {
        try {
            ObjectInputStream ois = new ObjectInputStream(new FileInputStream(
                    "obj.txt"));
            Person p = (Person) ois.readObject();
            System.out.println(p);
            ois.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    private static void writeObj() {
        try {
            ObjectOutputStream oos = new ObjectOutputStream(
                    new FileOutputStream("obj.txt"));
            oos.writeObject(new Person("zhangsan", 20));
            oos.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

class Person implements Serializable {

    String name;
    int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

}

五.管道流

package com.lgl.hellojava;

import java.io.IOException;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;

public class HelloJJAVA {
    public static void main(String[] args) {

        PipedInputStream pi = new PipedInputStream();
        PipedOutputStream po = new PipedOutputStream();

        try {
            pi.connect(po);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        Read read = new Read(pi);
        Write write = new Write(po);

        new Thread(read).start();
        new Thread(write).start();
    }
}

class Read implements Runnable {

    private PipedInputStream in;

    public Read(PipedInputStream in) {
        this.in = in;
    }

    @Override
    public void run() {
        try {
            byte[] buf = new byte[1024];
            int len = in.read(buf);
            String s = new String(buf, 0, len);
            System.out.println(s);
            in.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

}

class Write implements Runnable {

    private PipedOutputStream out;

    public Write(PipedOutputStream out) {
        this.out = out;
    }

    @Override
    public void run() {
        try {
            out.write("yes".getBytes());
            out.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}

六.RandomAccessFile

• 该类不是IO体系中的子类
• 但是他是IO包中的成员，他同时具备读写功能
• 内部封装了一个数组，而且通过指针对数组中的元素进行操作
• 可以通过getFilePointer或者指针位置同时可以通过seek改变指针的位置

package com.lgl.hellojava;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

public class HelloJJAVA {
    public static void main(String[] args) {
            writeFile();
    }

    public static void writeFile() {
        try {
            RandomAccessFile raf = new RandomAccessFile("1.txt", "rw");
            raf.write("zhangssan".getBytes());
            raf.writeInt(99);

            raf.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

private static void ReadFile() {
        try {
            RandomAccessFile raf = new RandomAccessFile("1.txt", "r");

            // 调整对象指针
            raf.seek(8 * 0);

            byte[] buf = new byte[1024];

            raf.read(buf);

            String s = new String(buf);

            System.out.println(s);

            raf.close();
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

七.IO其他类

• 操作基本数据类型
• 字节数组
• 字符数组

1.基本数据类型

    public static void readData() {
        try {
            DataInputStream dis = new DataInputStream(new FileInputStream(
                    "data.txt"));
            int num = dis.readInt();
            boolean d = dis.readBoolean();

            System.out.println(num + "" + d + "");

            dis.close();

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    // 基本数据类型
    public static void writeDatea() {
        try {
            DataOutputStream dos = new DataOutputStream(new FileOutputStream(
                    "data.txt"));

            dos.writeInt(55);
            dos.writeBoolean(true);

            dos.close();

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

二.字节数组

• ByteArrayInputStream： 在构造的时候，需要接收数据源，而且数据源是一个字节数组

• ByteArrayOutputStream：在构造的时候，不用定义数据的目的，因为该对象中已经内部封装了可变程度的字节数组

package com.lgl.hellojava;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

public class HelloJJAVA {
    public static void main(String[] args) {

        // 数据源
        ByteArrayInputStream bis = new ByteArrayInputStream("123".getBytes());
        // 数据目的
        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        int ch = 0;

        while ((ch = bis.read()) != -1) {
            bos.write(ch);
        }

        System.out.println(bos.size());
        System.out.println(bos.toString());

    }
}

八.字符编码

        String s = "hello java";
        byte [] b1 = s.getBytes();
        System.out.println(Arrays.toString(b1));

byte [] b1 = s.getBytes("GBK");

九.练习

• 有五个学生，每个学生有三门课程，从键盘输入以下数据（包括姓名，三门课成绩），输入的格式，如zhangsan,30,60,96计算出总成绩，并把学生的信息和计算出的总分数高低顺序存入文件student.txt中去；

package com.lgl.hellojava;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Set;
import java.util.TreeSet;

public class HelloJJAVA {
    public static void main(String[] args) {

        /**
         * 逻辑：
         * 1.通过获取键盘录入一行数据，然后取出数据封装成学生对象
         * 2.需要从高到低排列，需要排序，使用集合TreeSet就可以了
         * 3.写入文件
         */

        try {
            Set<Student> stus = StudentInfoTool.getStudents();
            StudentInfoTool.writeFile(stus);

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

// 比较数据，Comparable接口
class Student implements Comparable<Student> {

    // 姓名
    private String name;
    // 三科分数
    private int n1, n2, n3;
    // 总分
    private int sum;

    // 构造函数
    public Student(String name, int n1, int n2, int n3) {
        this.name = name;
        this.n1 = n1;
        this.n2 = n2;
        this.n3 = n3;
        sum = n1 + n2 + n3;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getSum() {
        return sum;
    }

    public void setSum(int sum) {
        this.sum = sum;
    }

    @Override
    public int compareTo(Student o) {
        int num = new Integer(this.sum).compareTo(new Integer(o.sum));
        if (num == 0) {
            return this.name.compareTo(o.name);
        }
        return num;
    }

    @Override
    public int hashCode() {
        // TODO Auto-generated method stub
        return name.hashCode() + sum * 78;
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof Student)) {
            throw new ClassCastException("Type Error");
        }
        Student s = (Student) obj;
        return this.name.equals(s.name) && this.sum == s.sum;
    }

}

// 工具类
class StudentInfoTool {
    public static Set<Student> getStudents() throws IOException {
        BufferedReader bufr = new BufferedReader(new InputStreamReader(
                System.in));
        String line = null;
        // 集合
        Set<Student> stus = new TreeSet<>();

        while ((line = bufr.readLine()) != null) {
            if (line.equals("over")) {
                break;
            }
            String[] info = line.split(",");
            Student student = new Student(info[0], Integer.parseInt(info[1]),
                    Integer.parseInt(info[2]), Integer.parseInt(info[3]));
            stus.add(student);
        }
        bufr.close();
        return stus;
    }

    // 写入文件
    public static void writeFile(Set<Student> stus) {
        try {
            BufferedWriter bufw = new BufferedWriter(new FileWriter(
                    "student.txt"));
            for (Student stu : stus) {
                bufw.write(stu.getName());
                bufw.write(stu.getSum() + "");
                bufw.newLine();
                bufw.flush();
            }

            bufw.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}

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