解 tar 指令

解壓縮 tar.gz
tar -zxvf xxxx.tar.gz

壓縮 tar.gz
tar -zcvf xxxx.tar.gz /folder

解壓縮 tar.bz2
tar -jxvf xxxx.tar.bz2

壓縮 tar.bz2
tar -jcvf xxxx.tar.bz2 /folder

解開 .tar
tar -xvf xxxx.tar

打包 .tar
tar -cvf xxxx.tar /folder

日期相減取得秒數

方法說明：

isHoliday() 方法判斷傳入日期是否為六日

getDuration() 方法回傳相減過後的秒數，包含六日

getTimeFrame() 方法回傳相減過後的秒數，不包含六日

/**

 * Check holiday

 *

 * @param startTime

 * @param endTime

 * @return true or false

 */

public static boolean isHoliday(Calendar calander) {

    boolean isHoliday = false;

    if (calander.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY

            && calander.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) {

        isHoliday = false;

    } else {

        isHoliday = true;

    }

    return isHoliday;

}

/**

 * Get the total seconds between the startTime & endTime

 *

 * @param startTime

 * @param endTime

 * @return

 */

public static long getDuration(Date startTime, Date endTime) {

    long totalSeconds = 0;

    Calendar startCal = Calendar.getInstance();

    startCal.setTime(startTime);

    Calendar endCal = Calendar.getInstance();

    endCal.setTime(endTime);

    totalSeconds = (endCal.getTimeInMillis() - startCal.getTimeInMillis()) / 1000;

    return totalSeconds;

}

/**

 * Get the total seconds between the startTime & endTime (Without Sunday &

 * Saturday)

 *

 * @param startTime

 * @param endTime

 * @return

 */

public static long getTimeFrame(Date startTime, Date endTime) {

    long timeFrame = 0;

    Calendar startCal = Calendar.getInstance();

    startCal.setTime(startTime);

    //startCal.add(Calendar.DATE, -6);

    Calendar endCal = Calendar.getInstance();

    endCal.setTime(endTime);

    //endCal.add(Calendar.DATE, 1);

    int useDays = 0;

    long totalSeconds = 0;

    Calendar tmpDate = Calendar.getInstance();

    tmpDate.setTimeInMillis(startCal.getTimeInMillis());

    if (DateUtils.isSameDate(startCal, endCal) && startCal.before(endCal)) {

        useDays = 0;

        totalSeconds = (endCal.getTimeInMillis() - startCal.getTimeInMillis()) / 1000;

        return totalSeconds;

    } else if (!DateUtils.isSameDate(startCal, endCal) && startCal.before(endCal)) {

        long secondsPastOfEndTime = endCal.get(Calendar.SECOND) + endCal.get(Calendar.MINUTE) * 60

                + endCal.get(Calendar.HOUR_OF_DAY) * 60 * 60;

        long secondsRemainOfStartTime = 0;

        while (tmpDate.before(endCal)) {

            tmpDate.add(Calendar.DATE, 1);

            if (DateUtils.isSameDate(tmpDate, endCal)) {

                break;

            } else {

                if (!MxDateUtility.isHoliday(startCal) && MxDateUtility.isHoliday(endCal)) {

                    useDays++;

                } else {

                    if (tmpDate.get(Calendar.DAY_OF_WEEK) != Calendar.SATURDAY

                            && tmpDate.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) {

                        useDays++;

                    }

                }

            }

        }

        if (MxDateUtility.isHoliday(startCal) && !MxDateUtility.isHoliday(endCal)) {

            secondsRemainOfStartTime = 0;

        } else {

            secondsRemainOfStartTime = 86400 - (startCal.get(Calendar.SECOND) + startCal.get(Calendar.MINUTE) * 60 + startCal

                    .get(Calendar.HOUR_OF_DAY) * 60 * 60);

        }

        long secondsOfUseDays = useDays * 86400;

        totalSeconds = secondsRemainOfStartTime + secondsOfUseDays + secondsPastOfEndTime;

        return totalSeconds;

    } else {

        return 0;

    }

}

List 排序

使用 Collections.sort(list) 方法
本方法只能針對 List<Integer> 及 List<String> 進行『升冪排序』
詳見<範例程式 1>及 <範例程式 2>

若要針對其它自訂 Object 物件進行排序
則必須將自訂 Object 宣告為實作 Comparator 之物件，並於 Class 實作 Compare() 方法
實作時可自定排序方式為『升冪』或『降冪』
詳見<範例程式 3>
本例子為升冪，修改 compare() 方法之第一個 if 判斷為
Long.parseLong(value2) - Long.parseLong(value1) > 0
即可轉為降冪排序

--------------範例程式 1--------------
    public static void main(String[] args) {

        List<Integer> list = new ArrayList<Integer>();

        list.add(4);

        list.add(1);

        list.add(3);

        list.add(2);

        Collections.sort(list);

        for (int value : list) {

            System.out.println(value);

        }

    }

範例程式 1 執行結果 ：
1
2
3
4

--------------範例程式 2--------------
    public static void main(String[] args) {

        List<String> list = new ArrayList<String>();

        list.add("d");

        list.add("a");

        list.add("c");

        list.add("b");

        Collections.sort(list);

        for (String value : list) {

            System.out.println(value);

        }

    }

範例程式 2 執行結果 ：
a
b
c
d

--------------範例程式 3--------------
<3-1>
import java.util.Comparator;

public class TestBean implements Comparator {

    String modifyDate;

    double value;

    public TestBean() {

    }

    public TestBean(String lastModifyDate, double averageTestValue) {

        this.modifyDate = lastModifyDate;

        this.value = averageTestValue;

    }

    @Override

    public int compare(Object obj1, Object obj2) {

        TestBean bean1 = (TestBean) obj1;

        TestBean bean2 = (TestBean) obj2;

        String value1 = bean1.getModifyDate();

        String value2 = bean2.getModifyDate();

        if (Long.parseLong(value1) - Long.parseLong(value2) > 0) {

            return 1;

        } else if (value1.equals(value2)) {

            return 0;

        } else {

            return -1;

        }

    }

    public String getModifyDate() {

        return modifyDate;

    }

    public void setModifyDate(String modifyDate) {

        this.modifyDate = modifyDate;

    }

    public double getValue() {

        return value;

    }

    public void setValue(double value) {

        this.value = value;

    }

}

<3-2>
import java.util.ArrayList;

import java.util.Collections;

import java.util.Comparator;

import java.util.List;

public class Test {

    public static void main(String[] args) {

        List<TestBean> testList = new ArrayList<TestBean>();

        testList.add(new TestBean("20130314000000", 1));

        testList.add(new TestBean("20130311000000", 2));

        testList.add(new TestBean("20130313000000", 3));

        testList.add(new TestBean("20130312130345", 4));

        testList.add(new TestBean("20130312110435", 5));

        Comparator comp = new TestBean();

        Collections.sort(testList, comp);

        for (TestBean a : testList) {

            System.out.println(a.getModifyDate() + ", " + a.getValue());

        }

    }

}

範例程式 3 執行結果 ：

20130311000000, 2.0
20130312110435, 5.0
20130312130345, 4.0
20130313000000, 3.0
20130314000000, 1.0

Oracle, SQL 以多個欄位為 Key, 取出 table 中另一欄位為 max 之資料

table_1 資料表如下圖：

如上資料表中，此資料表中並沒有設定 Primary Key欄位，但可由 column_1, column_2, column_3, column_4, column_5, column_6 的組合當成 Key 值，但仍有可能有重覆之資料，如表中所示，column_4 = 8 , 9 , 10 的資料都有多筆，但取資料時又希望依據相同的數據，將這些重覆的過濾掉只留下 check_column 數字最大的那筆時，可利用下面的SQL完成。

select *
from table_1
where (column_1, column_2, column_3, column_4, column_5, column_6, check_column)
in (
      select
          column_1,
          column_2,
          column_3,
          column_4,
          column_5,
          column_6,
          max(check_column)
       from table_1
       group by
          column_1,
          column_2,
          column_3,
          column_4,
          column_5,
          column_6
   )

結果如下圖：

Java 四捨五入至小數第 n 位

//欲四捨五入的數字
double y = 1.890784;

//設定要到小數第 3 位
int n = 3;

//執行四捨五入
double x = new BigDecimal(y).setScale(n, BigDecimal.ROUND_HALF_UP).doubleValue();

//印出結果
System.out.println(x);

//不要有科學記號出現的方法
double x = new BigDecimal(y).setScale(n, BigDecimal.ROUND_HALF_UP).toPlainString();

Java XPath 使用範例

XML 範例：books.xml

<?xml version="1.0" encoding="UTF-8"?>

<LIBRARY>

    <BOOKS>

        <BOOK isbn="ABCD7327923">

            <NAME>Java Programing</NAME>

            <SUBJECT>Java J2EE</SUBJECT>

            <AUTHORS>

                <AUTHOR>Tuna TORE</AUTHOR>

                <AUTHOR>Linus Torvalds</AUTHOR>

                <AUTHOR>James Gosling</AUTHOR>

            </AUTHORS>

        </BOOK>

        <BOOK isbn="DFGH09093232">

             <NAME>XPATH for Dummies</NAME>

           <SUBJECT> XPATH development</SUBJECT>

            <AUTHORS>

                <AUTHOR>Linus Torvalds</AUTHOR>

                <AUTHOR>John Hawking</AUTHOR>

            </AUTHORS>

        </BOOK>

        <BOOK isbn="DSKL2393A">

            <NAME>J2EE Patterns</NAME>

            <SUBJECT>Design Patterns</SUBJECT>

            <AUTHORS>

                <AUTHOR>Aka Tuna</AUTHOR>

            </AUTHORS>

        </BOOK>

    </BOOKS>

    <DVDS>

        <DVD id="123456">

            <NAME>Music DVD</NAME>

            <CONTENT>Music</CONTENT>

            <AUTHORS>

                <AUTHOR>James Gosling</AUTHOR>

                <AUTHOR>Bill Gates</AUTHOR>

            </AUTHORS>

        </DVD>

        <DVD id="3213324">

            <NAME>Natural Science</NAME>

            <CONTENT>Science</CONTENT>

            <AUTHORS>

                <AUTHOR>John Green</AUTHOR>

                <AUTHOR>Bill Gates</AUTHOR>

            </AUTHORS>

        </DVD>

        <DVD id="4353534">

            <NAME>Rally</NAME>

            <CONTENT>Race</CONTENT>

            <AUTHORS>

                <AUTHOR>Tuna</AUTHOR>

            </AUTHORS>

        </DVD>

    </DVDS>

</LIBRARY>

程式範例： XpathTest.java

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.xpath.XPath;

import javax.xml.xpath.XPathConstants;

import javax.xml.xpath.XPathExpression;

import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;

import org.w3c.dom.NodeList;

public class XPathTest {

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

        //loading the XML document from a file

        DocumentBuilderFactory builderfactory = DocumentBuilderFactory.newInstance();

        builderfactory.setNamespaceAware(true);

        DocumentBuilder builder = builderfactory.newDocumentBuilder();

        Document xmlDocument = builder.parse("src\\books.xml");

        XPathFactory factory = javax.xml.xpath.XPathFactory.newInstance();

        XPath xPath = factory.newXPath();

        //getting the name of the book having an isbn number == ABCD7327923

        String isbnNum = "ABCD7327923";

        XPathExpression xPathExpression = xPath.compile("//LIBRARY//BOOKS//BOOK[@isbn='" + isbnNum + "']//NAME");

        String nameOfTheBook = xPathExpression.evaluate(xmlDocument, XPathConstants.STRING).toString();

        System.out.println("name of the Book ---> " + nameOfTheBook);

        //getting all authors for the book having an isbn number == ABCD7327923

        xPathExpression = xPath.compile("//LIBRARY//BOOKS//BOOK[@isbn='" + isbnNum + "']//AUTHORS//AUTHOR");

        NodeList nodeListBook = (NodeList) xPathExpression.evaluate(xmlDocument, XPathConstants.NODESET);

        System.out.println("Total number of authors for the book " + nameOfTheBook + " is --> "

                + nodeListBook.getLength());

        for (int index = 0; index < nodeListBook.getLength(); index++) {

            String author = nodeListBook.item(index).getTextContent();

            System.out.println("Author " + (index + 1) + " ---> " + author);

        }

        //getting all tags for the dvd having id == 3213324

        String dvdID = "3213324";

        xPathExpression = xPath.compile("//LIBRARY//DVDS//DVD[@id='" + dvdID + "']");

        NodeList nodeDVD = (NodeList) xPathExpression.evaluate(xmlDocument, XPathConstants.NODESET);

        NodeList nodeListForDVD = nodeDVD.item(0).getChildNodes();

        for (int index = 0; index < nodeDVD.item(0).getChildNodes().getLength(); index++) {

            String tagName = nodeListForDVD.item(index).getNodeName();

            String tagValue = nodeListForDVD.item(index).getTextContent();

            if (!tagName.equals("#text")) //handling empty comment (#text)

                System.out.println(tagName + " value ---> " + tagValue);

        }

    }

}

執行結果：
name of the Book: Java Programing
Total number of authors for the book Java Programing is --> 3
Author 1: Tuna TORE
Author 2: Linus Torvalds
Author 3: James Gosling
NAME value: Natural Science
CONTENT value: Science
AUTHORS value:
                John Green
                Bill Gates

參考文件：http://tunatore.wordpress.com/2011/05/20/how-to-use-xpath-i-java-simple-example/