20个非常有用的Java程序片段（三）
17. 把Array 转换成 Map
1.import java.util.Map;
2.import org.apache.commons.lang.ArrayUtils;
3.
4.public class Main {
5.
6. public static void main(String[] args) {
7. String[][] countries = { { "United States", "New York" }, { "United Kingdom", "London" },
8. { "Netherland", "Amsterdam" }, { "Japan", "Tokyo" }, { "France", "Paris" } };
9.
10. Map countryCapitals = ArrayUtils.toMap(countries);
11.
12. System.out.println("Capital of Japan is " + countryCapitals.get("Japan"));
13. System.out.println("Capital of France is " + countryCapitals.get("France"));
14. }
15.}
18. 发送邮件
1.import javax.mail.*;
2.import javax.mail.internet.*;
3.import java.util.*;
4.
5.publicvoid postMail( String recipients[ ], String subject, String message , String from) throws MessagingException
6.{
7.boolean debug = false;
8.
9.//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
1.import java.io.BufferedReader;
2.import java.io.InputStreamReader;
3.import java.net.URL;
4.
5.publicclass Main {
6.publicstaticvoid main(String[] args) {
7.try {
8. URL my_url = new URL("http://coolshell.cn/");
9. BufferedReader br = new BufferedReader(new InputStreamReader(my_url.openStream()));
10. String strTemp = "";
11.while(null != (strTemp = br.readLine())){
12. System.out.println(strTemp);
13. }
14. } catch (Exception ex) {
15. ex.printStackTrace();
16. }
17. }
18.}
20. 改变数组的大小
1./**
2.* Reallocates an array with a new size, and copies the contents
3.* of the old array to the new array.
4.* @param oldArray the old array, to be reallocated.
5.* @param newSize the new array size.
6.* @return A new array with the same contents.
7.*/
8.privatestatic Object resizeArray (Object oldArray, int newSize) {
9.int oldSize = java.lang.reflect.Array.getLength(oldArray);
10. Class elementType = oldArray.getClass().getComponentType();
11. Object newArray = java.lang.reflect.Array.newInstance(
12. elementType,newSize);
13.int preserveLength = Math.min(oldSize,newSize);
14.if (preserveLength > 0)
15. System.arraycopy (oldArray,0,newArray,0,preserveLength);
16.return newArray;
17.}
18.
19.// Test routine for resizeArray().
20.publicstaticvoid main (String[] args) {
21.int[] a = {1,2,3};
22. a = (int[])resizeArray(a,5);
23. a[3] = 4;
24. a[4] = 5;
25.for (int i=0; i<a.length; i++)
26. System.out.println (a[i]);
}