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标题: （整理and分享）20个JAVA人员非常有用的功能代码 第二部分 [打印本页]

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作者: xbs783    时间: 2016-11-3 18:27
标题: （整理and分享）20个JAVA人员非常有用的功能代码 第二部分
此为第二部分，第一部分链接请点击！！！
（整理and分享）20个JAVA人员非常有用的功能代码 第一部分
http://bbs.itheima.com/forum.php?mod=viewthread&tid=332865
(出处: 黑马程序员IT技术论坛)

15. 在Java中创建ZIP和JAR文件
import java.util.zip.*;
import java.io.*;

public class ZipIt {
public static void main(String args []) throws IOException {
if (args.length < 2) {
System.err.println("usage: java ZipIt Zip.zip file1 file2 file3");
System.exit(-1);
}
File zipFile = new File(args [0]);
if (zipFile.exists()) {
System.err.println("Zip file already exists, please try another");
System.exit(-2);
}
FileOutputStream fos = new FileOutputStream(zipFile);
ZipOutputStream zos = new ZipOutputStream (fos);
int bytesRead;
byte[] buffer = new byte [1024];
CRC32 crc = new CRC32 ();
for (int i=1, n=args.length; i < n; i++) {
String name = args;
File file = new File (name);
if (!file.exists()) {
   System.err.println("Skipping: " + name);
& nbsp;   continue;
}
BufferedInputStream bis = new BufferedInputStream (
   new FileInputStream (file));
crc.reset();
while ((bytesRead = bis.read(buffer)) != -1) {
   crc.update(buffer, 0, bytesRead);
}
bis.close ();
// Reset to beginning of input stream
bis = new BufferedInputStream (
   new FileInputStream (file));
ZipEntry entry = new ZipEntry (name);
entry.setMethod (ZipEntry.STORED);
& nbsp; entry.setCompressedSize(file.length ());
entry.setSize(file.length ());
entry.setCrc(crc.getValue ());
zos.putNextEntry (entry);
while ((bytesRead = bis.read(buffer)) != -1) {
   zos.write(buffer, 0, bytesRead);
}
bis.close ();
}
zos.close();
}
}
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16. Parsing / Reading XML file in Java
Sample XML file.
//...

package net.viralpatel.java.xmlparser;

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class XMLParser {

public void getAllUserNames(String fileName) {
try {
DocumentBuilderFactory dbf =

DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
File file = new File (fileName);
if (file.exists()) {
Document doc = db.parse (file);
Element docEle = doc.getDocumentElement();

// Print root element of the document
System.out.println("Root element of the document: "
+ docEle.getNodeName());

NodeList studentList = docEle.getElementsByTagName

("student");

// Print total student elements in document
System.out
&nb sp;.println("Total students: " +

studentList.getLength());

if (studentList != null && studentList.getLength()

> 0) {
for (int i = 0; i < studentList.getLength

(); i++) {

Node node = studentList.item(i);

if (node.getNodeType() ==

Node.ELEMENT_NODE) {

System.out
     .println

("=====================");

Element e = (Element) node;
NodeList nodeList =

e.getElementsByTagName ("name");
System.out.println("Name: "
+

nodeList.item(0).getChildNodes().item(0)

.getNodeValue());

nodeList =

e.getElementsByTagName ("grade");
System.out.println("Grade:

"
+

nodeList.item(0).getChildNodes().item(0)

.getNodeValue());

nodeList =

e.getElementsByTagName ("age");
System.out.println("Age: "
+

nodeList.item(0).getChildNodes().item(0)

.getNodeValue());
}
}
} else {
System.exit(1);
}
}
} catch (Exception e) {
System.out.println(e);
}
}
public static void main(String[] args) {

XMLParser parser = new XMLParser ();
parser.getAllUserNames("c:\\test.xml");
}
}
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17. Convert Array to Map in Java
import java.util.Map;
import org.apache.commons.lang.ArrayUtils;

public class Main {

public static void main(String[] args) {
String[][] countries = { { "United States", "New York" }, { "United Kingdom",

"London" },
{ "Netherland", "Amsterdam" }, { "Japan", "Tokyo" }, { "France", "Paris" }

};

Map countryCapitals = ArrayUtils.toMap(countries);

System.out.println("Capital of Japan is " + countryCapitals.get("Japan"));
System.out.println("Capital of France is " + countryCapitals.get("France"));
}
}
复制代码
18. Send Email using Java

import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;

public void postMail( String recipients[ ], String subject, String message , String

from) throws MessagingException
{
boolean debug = false;

//Set the host smtp address
Properties props = new Properties();
props.put ("mail.smtp.host", "smtp.example.com");

// create some properties and get the default Session
Session session = Session.getDefaultInstance(props, null);
session.setDebug(debug);

// create a message
Message msg = new MimeMessage(session);

// set the from and to address
InternetAddress addressFrom = new InternetAddress(from);
msg.setFrom(addressFrom);

InternetAddress[] addressTo = new InternetAddress [recipients.length];
for (int i = 0; i < recipients.length; i++)
{
addressTo = new InternetAddress (recipients);
}
msg.setRecipients (Message.RecipientType.TO, addressTo);

// Optional : You can also set your custom headers in the Email if you Want
msg.addHeader("MyHeaderName", "myHeaderValue");

// Setting the Subject and Content Type
msg.setSubject(subject);
msg.setContent(message, "text/plain");
Transport.send(msg);
}
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19. Send HTTP request & fetching data using Java
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;

public class Main {
public static void main(String[] args)  {
try {
URL my_url = new URL("http://www.viralpatel.net/blogs/");
   BufferedReader br = new BufferedReader(new

InputStreamReader(my_url.openStream()));
String strTemp = "";
while(null != (strTemp = br.readLine())) {
System.out.println(strTemp);
}
} catch (Exception ex) {
ex.printStackTrace ();
}
}
}
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20. Resize an Array in Java
/**
* Reallocates an array with a new size, and copies the contents
* of the old array to the new array.
* @param oldArray  the old array, to be reallocated.
* @param newSize   the new array size.
* @return          A new array with the same contents.
*/
private static Object resizeArray (Object oldArray, int newSize) {  
int oldSize = java.lang.reflect.Array.getLength(oldArray);  
Class elementType = oldArray.getClass().getComponentType();  
Object newArray = java.lang.reflect.Array.newInstance(  
elementType,newSize);  
int preserveLength = Math.min (oldSize,newSize);  
if (preserveLength > 0)   
System.arraycopy (oldArray,0,newArray,0,preserveLength);  
return newArray;  
}  

// Test routine for resizeArray().  
public static void main (String[] args) {  
int[] a = {1,2,3};  
a = (int[])resizeArray(a,5);  
a[3] = 4;  
a[4] = 5;  
for (int i=0; i
      System.out.println (a);  
}
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16. 在Java中解析/读取XML文件
view plaincopy to clipboardprint?

<?xml version="1.0"?>  
<students>  
<student>  
<name>John</name>  
<grade>B</grade>  
<age>12</age>  
</student>  
<student>  
<name>Mary</name>  
<grade>A</grade>  
<age>11</age>  
</student>  
<student>  
<name>Simon</name>  
<grade>A</grade>  
<age>18</age>  
</student>  
</students>  



<?xml version="1.0"?>
<students>
<student>
<name>John</name>
<grade>B</grade>
<age>12</age>
</student>
<student>
<name>Mary</name>
<grade>A</grade>
<age>11</age>
</student>
<student>
<name>Simon</name>
<grade>A</grade>
<age>18</age>
</student>
</students>
Java code to parse above XML.

view plaincopy to clipboardprint?

package net.viralpatel.java.xmlparser;

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class XMLParser {

public void getAllUserNames(String fileName) {
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
File file = new File(fileName);
if (file.exists()) {
Document doc = db.parse(file);
Element docEle = doc.getDocumentElement();

// Print root element of the document
System.out.println("Root element of the document: "
+ docEle.getNodeName());

NodeList studentList = docEle.getElementsByTagName("student");

// Print total student elements in document
System.out
.println("Total students: " + studentList.getLength());

if (studentList != null && studentList.getLength() > 0) {
for (int i = 0; i < studentList.getLength(); i++) {

Node node = studentList.item(i);

if (node.getNodeType() == Node.ELEMENT_NODE) {

System.out
.println("=====================");

Element e = (Element) node;
NodeList nodeList = e.getElementsByTagName("name");
System.out.println("Name: "
+ nodeList.item(0).getChildNodes().item(0)
.getNodeValue());

nodeList = e.getElementsByTagName("grade");
System.out.println("Grade: "
+ nodeList.item(0).getChildNodes().item(0)
.getNodeValue());

nodeList = e.getElementsByTagName("age");
System.out.println("Age: "
+ nodeList.item(0).getChildNodes().item(0)
.getNodeValue());
}
}
} else {
System.exit(1);
}
}
} catch (Exception e) {
System.out.println(e);
}
}
public static void main(String[] args) {

XMLParser parser = new XMLParser();
parser.getAllUserNames("c:\\test.xml");
}
}
复制代码
17. 在Java中将Array转换成Map
view plaincopy to clipboardprint?

import java.util.Map;
import org.apache.commons.lang.ArrayUtils;

public class Main {

public static void main(String[] args) {
String[][] countries = { { "United States", "New York" }, { "United Kingdom", "London" },
{ "Netherland", "Amsterdam" }, { "Japan", "Tokyo" }, { "France", "Paris" } };

Map countryCapitals = ArrayUtils.toMap(countries);

System.out.println("Capital of Japan is " + countryCapitals.get("Japan"));
System.out.println("Capital of France is " + countryCapitals.get("France"));
}
}
复制代码
18. 在Java中发送电子邮件
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import javax.mail.*;
import javax.mail.internet.*;
import java.util.*;

public void postMail( String recipients[ ], String subject, String message , String from) throws MessagingException
{
boolean debug = false;

//Set the host smtp address
Properties props = new Properties();
props.put("mail.smtp.host", "smtp.example.com");

// create some properties and get the default Session
Session session = Session.getDefaultInstance(props, null);
session.setDebug(debug);

// create a message
Message msg = new MimeMessage(session);

// set the from and to address
InternetAddress addressFrom = new InternetAddress(from);
msg.setFrom(addressFrom);

InternetAddress[] addressTo = new InternetAddress[recipients.length];
for (int i = 0; i < recipients.length; i++)
{
addressTo = new InternetAddress(recipients);
}
msg.setRecipients(Message.RecipientType.TO, addressTo);

// Optional : You can also set your custom headers in the Email if you Want
msg.addHeader("MyHeaderName", "myHeaderValue");

// Setting the Subject and Content Type
msg.setSubject(subject);
msg.setContent(message, "text/plain");
Transport.send(msg);
}
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19. 使用Java发送HTTP请求和提取数据
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import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;

public class Main {
public static void main(String[] args)  {
try {
URL my_url = new URL("http://www.viralpatel.net/blogs/");
BufferedReader br = new BufferedReader(new InputStreamReader(my_url.openStream()));
String strTemp = "";
while(null != (strTemp = br.readLine())){
System.out.println(strTemp);
}
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
复制代码
20. 在Java中调整数组
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/**  
* Reallocates an array with a new size, and copies the contents  
* of the old array to the new array.  
* @param oldArray  the old array, to be reallocated.  
* @param newSize   the new array size.  
* @return          A new array with the same contents.  
*/  
private static Object resizeArray (Object oldArray, int newSize) {   
int oldSize = java.lang.reflect.Array.getLength(oldArray);   
Class elementType = oldArray.getClass().getComponentType();   
Object newArray = java.lang.reflect.Array.newInstance(   
elementType,newSize);   
int preserveLength = Math.min(oldSize,newSize);   
if (preserveLength > 0)   
System.arraycopy (oldArray,0,newArray,0,preserveLength);   
return newArray;   
}   

// Test routine for resizeArray().   
public static void main (String[] args) {   
int[] a = {1,2,3};   
a = (int[])resizeArray(a,5);   
a[3] = 4;   
a[4] = 5;   
for (int i=0; i<a.length; i++)   
System.out.println (a);   
}

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作者: GXM    时间: 2016-11-3 21:46
赞。。

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