20非常有用的Java程序片段 (下)

17. 把 Array 转换成 Map 

view source

<embed id="highlighter_896067_clipboard" title="copy to clipboard" type="application/x-shockwave-flash" width="16" height="16" src="http://cocre.com/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" lk_media="yes" lk_mediaid="lk_juiceapp_mediaPopup_1243315889047" allowscriptaccess="always" wmode="transparent" flashvars="highlighterId=highlighter_896067" menu="false"></embed>

print ?

01.    

02. import java.util.Map;  

03. import org.apache.commons.lang.ArrayUtils;  

04.    

05. public class Main {  

06.    

07.    public static void main(String[] args) {  

08.      String[][] countries = { { "United States" , "New York" }, { "United Kingdom" , "London" },  

09.          { "Netherland" , "Amsterdam" }, { "Japan" , "Tokyo" }, { "France" , "Paris" } };  

10.    

11.      Map countryCapitals = ArrayUtils.toMap(countries);  

12.    

13.      System.out.println( "Capital of Japan is " + countryCapitals.get( "Japan" ));  

14.      System.out.println( "Capital of France is " + countryCapitals.get( "France" ));  

15.    }  

16. } 

18. 发送邮件

view source

<embed id="highlighter_191237_clipboard" title="copy to clipboard" type="application/x-shockwave-flash" width="16" height="16" src="http://cocre.com/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" lk_media="yes" lk_mediaid="lk_juiceapp_mediaPopup_1243315889051" allowscriptaccess="always" wmode="transparent" flashvars="highlighterId=highlighter_191237" menu="false"></embed>

print ?

01. import javax.mail.*;  

02. import javax.mail.internet.*;  

03. import java.util.*;  

04.    

05. public void postMail( String recipients[ ], String subject, String message , String from) throws MessagingException  

06. {  

07.      boolean debug = false ;  

08.    

09.       //Set the host smtp address  

10.       Properties props = new Properties();  

11.       props.put( "mail.smtp.host" , "smtp.example.com" );  

12.    

13.      // create some properties and get the default Session  

14.      Session session = Session.getDefaultInstance(props, null );  

15.      session.setDebug(debug);  

16.    

17.      // create a message  

18.      Message msg = new MimeMessage(session);  

19.    

20.      // set the from and to address  

21.      InternetAddress addressFrom = new InternetAddress(from);  

22.      msg.setFrom(addressFrom);  

23.    

24.      InternetAddress[] addressTo = new InternetAddress[recipients.length];  

25.      for ( int i = 0 ; i < recipients.length; i++)  

26.      {  

27.          addressTo[i] = new InternetAddress(recipients[i]);  

28.      }  

29.      msg.setRecipients(Message.RecipientType.TO, addressTo);  

30.    

31.      // Optional : You can also set your custom headers in the Email if you Want  

32.      msg.addHeader( "MyHeaderName" , "myHeaderValue" );  

33.    

34.      // Setting the Subject and Content Type  

35.      msg.setSubject(subject);  

36.      msg.setContent(message, "text/plain" );  

37.      Transport.send(msg);  

38. } 

19. 发送代数据的HTTP 请求

view source

<embed id="highlighter_334990_clipboard" title="copy to clipboard" type="application/x-shockwave-flash" width="16" height="16" src="http://cocre.com/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" lk_media="yes" lk_mediaid="lk_juiceapp_mediaPopup_1243315889055" allowscriptaccess="always" wmode="transparent" flashvars="highlighterId=highlighter_334990" menu="false"></embed>

print ?

01.    

02. import java.io.BufferedReader;  

03. import java.io.InputStreamReader;  

04. import java.net.URL;  

05.    

06. public class Main {  

07.      public static void main(String[] args)  {  

08.          try {  

09.              URL my_url = new URL( "http://cocre.com/ " );  

10.              BufferedReader br = new BufferedReader( new InputStreamReader(my_url.openStream()));  

11.              String strTemp = "" ;  

12.              while ( null != (strTemp = br.readLine())){  

13.              System.out.println(strTemp);  

14.          }  

15.          } catch (Exception ex) {  

16.              ex.printStackTrace();  

17.          }  

18.      }  

19. }

20. 改变数组的大小

view source

<embed id="highlighter_818592_clipboard" title="copy to clipboard" type="application/x-shockwave-flash" width="16" height="16" src="http://cocre.com/wp-content/plugins/syntaxhighlighter/syntaxhighlighter/scripts/clipboard.swf" lk_media="yes" lk_mediaid="lk_juiceapp_mediaPopup_1243315889059" allowscriptaccess="always" wmode="transparent" flashvars="highlighterId=highlighter_818592" menu="false"></embed>

print ?

01.    

02. /** 

03. * Reallocates an array with a new size, and copies the contents 

04. * of the old array to the new array. 

05. * @param oldArray  the old array, to be reallocated. 

06. * @param newSize   the new array size. 

07. * @return          A new array with the same contents. 

08. */  

09. private static Object resizeArray (Object oldArray, int newSize) {  

10.     int oldSize = java.lang.reflect.Array.getLength(oldArray);  

11.     Class elementType = oldArray.getClass().getComponentType();  

12.     Object newArray = java.lang.reflect.Array.newInstance(  

13.           elementType,newSize);  

14.     int preserveLength = Math.min(oldSize,newSize);  

15.     if (preserveLength > 0 )  

16.        System.arraycopy (oldArray, 0 ,newArray, 0 ,preserveLength);  

17.     return newArray;  

18. }  

19.    

20. // Test routine for resizeArray().  

21. public static void main (String[] args) {  

22.     int [] a = { 1 , 2 , 3 };  

23.     a = ( int [])resizeArray(a, 5 );  

24.     a[ 3 ] = 4 ;  

25.     a[ 4 ] = 5 ;  

26.     for ( int i= 0 ; i<a.length; i++)  

27.        System.out.println (a[i]);  

28. }