使用過濾流(高階流)BufferedInputStream、BufferedInputStream優化檔案拷貝功能

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

/**
 * @author cuijiao
 *
 */
public class Filestream
 
 {

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

        File src = new File("D:\\data\\test.jpg");
        File target = new File("E:\\copy.jpg");
        copyFileByBuffer(src, target);

    }

    /**
     * 拷貝檔案：將src複製到target
     *
     * @param src
     * @param target
     * @throws
 
 IOException
     */
    private static void copyFileByBuffer(File src, File target) throws IOException {
        if (!src.exists()) {
            return;
        }
        if (!target.exists()) {
            target.createNewFile();
        }
        FileInputStream fis = null;
        FileOutputStream fos = null
 
;
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;
        // 優先使用高階流，速度快
        fis = new FileInputStream(src);
        bis = new BufferedInputStream(fis);
        fos = new FileOutputStream(target);
        bos = new BufferedOutputStream(fos);
        byte[] buf = new byte[1024];
        int lenth = -1;
        lenth = bis.read(buf);// 讀
        while (lenth != -1) {
            bos.write(buf, 0, lenth);// 寫
            lenth = bis.read(buf);// 讀
        }
        // 先關高階流
        // 實際上關閉高階流的同時，低階流也會被關掉了
        bis.close();
        bos.close();
        fis.close();
        fos.close();

    }

}

FileInputStream——BufferedInputStream——DataInputStream一層包一層，不斷給管子加粗，提升讀寫速度

物件流ObjectInputStream 、ObjectOutputStream

只能將支援 java.io.Serializable 介面的物件寫入流中。每個 serializable 物件的類都被編碼，編碼內容包括類名和類簽名、物件的欄位值和陣列值，以及從初始物件中引用的其他所有物件的閉包。

writeObject 方法用於將物件寫入流中。所有物件（包括 String 和陣列）都可以通過 writeObject 寫入。可將多個物件或基元寫入流中。必須使用與寫入物件時相同的型別和順序從相應 ObjectInputstream 中讀回物件。

import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Date;

/**
 * @author cuijiao 物件流，ObjectOutputStream可用於物件的持久化操作
 */
public class ObjectStream {

    /**
     * @param args
     * @throws IOException
     */
    public static void main(String[] args) {
        // 寫物件
        // writeObject();
        // 讀物件
        readObject();
    }

    /**
     *
     * 物件必須序列化並有序列號
     */
    private static void readObject() {
        // TODO Auto-generated method stub
        File file = new File("D:\\data\\test.log");
        if (!file.exists()) {
            return;
        }
        FileInputStream fis = null;
        ObjectInputStream ois = null;
        Emp emp = null;
        try {
            fis = new FileInputStream(file);
            ois = new ObjectInputStream(fis);
            try {
                emp = (Emp) ois.readObject();// 讀到最後無資料時，不是返回物件而是報EOFException
                while (emp != null) {
                    System.out.println(emp);
                    emp = (Emp) ois.readObject();
                }
            } catch (EOFException e) {
                // EOFException異常，表示讀資料結束，不需要任何操作
            }

        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } finally {
            try {
                ois.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

    /**
     * 序列化，對於需要用writeObject寫入檔案的物件，必須要實現序列化
     */
    private static void writeObject() {
        File file = new File("D:\\data\\test.log");
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        FileOutputStream fos = null;
        ObjectOutputStream oos = null;
        Emp emp = new Emp("lisa", "e001", 888, true, new Date());

        try {
            fos = new FileOutputStream(file);
            oos = new ObjectOutputStream(fos);
            oos.writeObject(emp);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                oos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

}

其中需要讀寫的物件emp，必須實現序列化；

import java.io.Serializable;
import java.util.Date;

public class Emp implements Serializable {

    /**
     * defalut serialVersionUID
     */
    private static final long serialVersionUID = 1L;

    private String empName;

    private String empNo;

    private double salary;

    private boolean sex;

    private Date birthday;

    /**
     * default constructor
     */
    public Emp() {

    }

    /**
     * max constructor
     */
    public Emp(String empName, String empNo, double salary, boolean sex, Date birthday) {
        this.empName = empName;
        this.empNo = empNo;
        this.salary = salary;
        this.sex = sex;
        this.birthday = birthday;
    }

    /**
     * min constructors
     */
    public Emp(String empNo) {
        this.empNo = empNo;
    }

    public String getEmpName() {
        return empName;
    }

    public void setEmpName(String empName) {
        this.empName = empName;
    }

    public String getEmpNo() {
        return empNo;
    }

    public void setEmpNo(String empNo) {
        this.empNo = empNo;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public boolean isSex() {
        return sex;
    }

    public void setSex(boolean sex) {
        this.sex = sex;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "Emp [ 姓名：" + empName + ", 員工號：" + empNo + ", 薪資：" + salary + ", 性別：" + (sex ? "男" : "女") + ", 生日：" + DateUtil.date2Sring(birthday) + "]";
    }

}

java已有的類，大多已經實現了序列化，對於我們自己定義的類，需要實現序列號，並給預設的序列化即可。