Java學習記錄(補充八:Date類;Java流(Stream),檔案(File)和IO)

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Date類,Calendar類
package Box1;import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Calendar;import java.util.Date;import java.util.Random;//Date類public class DateTest {    public static void main(String[] args) {        Date date = new Date();        System.out.println(date);        //System.out.println(date.getYear());                //格式化時間        SimpleDateFormat sf= new SimpleDateFormat("yyyy年MM-dd hh:mm:ss E");        String dateString = sf.format(date);        System.out.println(dateString);                //練習:寫一個方法，自動產生定單編號，規則：前2個字元為je         //後邊14位為當前日期及時間，後面是四位隨機數.        //例如：je201708291456201890        SimpleDateFormat change = new SimpleDateFormat("yyyyMMddhhmmss");        String changeDate = change.format(date);        Random a = new Random();        int a1 = a.nextInt(10);        int a2 = a.nextInt(10);        int a3 = a.nextInt(10);        int a4 = a.nextInt(10);        System.out.println("je"+changeDate+a1+a2+a3+a4);                        //Calendar是抽象類別,不能執行個體化,        //能通過調用靜態方法來執行個體化,用來產生對象的靜態方法,一般稱為Factory 方法        Calendar c= Calendar.getInstance();                System.out.print(c.get(Calendar.YEAR)+"-");        System.out.print(c.get(Calendar.MONTH)+1+"-");        System.out.print(c.get(Calendar.DATE)+" ");        System.out.print(c.get(Calendar.HOUR)+":");        System.out.print(c.get(Calendar.MINUTE)+":");        System.out.print(c.get(Calendar.SECOND)+" ");        System.out.println(c.get(Calendar.DAY_OF_WEEK));//星期日是1                //date與calendar互轉        Date d1 = c.getTime();        System.out.println(sf.format(d1));                c.setTime(date);                //日期的計算        Calendar c1 = Calendar.getInstance();        //第一個參數:要加那個欄位        //第二個參數:要加多少        c1.add(Calendar.DATE, 100);        Date d2 = c1.getTime();        System.out.println(sf.format(d2));                            //日期與字串互轉        //Date轉String用SimpleDateFormat        Date d3 = new Date("2017/8/9");//格式不對會報錯        long d4= Date.parse("2017/10/10");        Date d5 = new Date();        d5.setTime(d4);                //把字串轉成Date        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");        try {            Date d6=format.parse("2017-08-09");            System.out.println(d6);        } catch (ParseException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }                                        Calendar c2 = Calendar.getInstance();        c2.set(2017, 9, 27, 20, 20,12);                    }}

結果圖:

 

枚舉
package Box1;//枚舉:表示常量,提高代碼的可讀性public enum Week {    MON,TUE,WED,THU,SAT,SUN}

package Box1;public class WeekTestEnum {    public static void main(String[] args) {            System.out.println(Week.MON);            Week n =Week.MON;            switch (n) {            case MON:                System.out.println("周一");                break;            case TUE:                System.out.println("周二");                break;            default:                break;            }                    }}

結果圖:

 

 

單例模式(重點)

 

 

 

 

Java流(Stream),檔案(File)和IO

package com.jredu.iodemo;//Java 流(Stream)、檔案(File)和IOimport java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;public class IOTest {    public static void main(String[] args) {        try {            FileInputStream fis=                    new FileInputStream("G:/IO資料/io.text.txt");//調用文檔            //磁碟目錄下的文檔            byte[]data = new byte[1024];            int len;            while((len=fis.read(data))!=-1){                String s=new String(data,0,len);                System.out.println(s);            }            fis.close();        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        try {            FileOutputStream fos =                     new FileOutputStream("G:/IO資料/io.text.txt");            fos.write("abc".getBytes());//直接覆蓋裡面的內容            fos.flush();            fos.close();        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }                                    }}

結果圖::

package com.jredu.iodemo;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;public class FileCopyDemo {    public static void main(String[] args) {        try {            FileInputStream fis = new FileInputStream("G:/IO資料/123.png");            FileOutputStream fos = new FileOutputStream("G:/IO資料/1234.png");                        byte []data = new byte[1024];            int len;            try {                while((len=fis.read(data))!=-1){                    fos.write(data,0,len);                }                fis.close();                fos.flush();                fos.close();                System.out.println(" copy OK!");            } catch (IOException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }                    } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }            }}

結果圖:

 

Java學習記錄(補充八:Date類;Java流(Stream),檔案(File)和IO)