BlogJava-aijava-文章分类-java基础学习系列

java基础学习16(java.io.DataOutputStream)

Sun, 12 Nov 2006 15:21:00 GMT

import java.io.DataOutputStream;
import java.io.FileOutputStream;

public class MainClass {

   public static void main ( String args []) {
     try {

       FileOutputStream fos = new FileOutputStream ("fileName" ) ;

       DataOutputStream dos = new DataOutputStream ( fos ) ;

       dos.writeBoolean ( false ) ;
       dos.writeByte ( Byte.MAX_VALUE ) ;
       dos.writeChar ( 'A' ) ;
       dos.writeDouble ( Double.MAX_VALUE ) ;
       dos.writeFloat ( Float.MAX_VALUE ) ;
       dos.writeInt ( Integer.MAX_VALUE ) ;
       dos.writeLong ( Long.MAX_VALUE ) ;
       dos.writeShort ( Short.MAX_VALUE ) ;

       fos.close () ;
     } catch ( Exception e ) {
       System.out.println ( "Exception: " + e ) ;
     }
   }
}

苑 2006-11-12 23:21 发表评论

java基础学习15(java.io.DataInputStream)

Sun, 12 Nov 2006 15:19:00 GMT

import java.io.DataInputStream;
import java.io.FileInputStream;

public class MainClass {

   public static void main ( String args []) {
     try {

       FileInputStream fis = new FileInputStream ( "fileName.dat" ) ;

       // Create a data input stream
       DataInputStream dis = new DataInputStream ( fis ) ;

       // Read and display data
       System.out.println ( dis.readBoolean ()) ;
       System.out.println ( dis.readByte ()) ;
       System.out.println ( dis.readChar ()) ;
       System.out.println ( dis.readDouble ()) ;
       System.out.println ( dis.readFloat ()) ;
       System.out.println ( dis.readInt ()) ;
       System.out.println ( dis.readLong ()) ;
       System.out.println ( dis.readShort ()) ;

       // Close file input stream
       fis.close () ;
     } catch ( Exception e ) {
       System.out.println ( "Exception: " + e ) ;
     }
   }
}

苑 2006-11-12 23:19 发表评论

java基础学习14(java.io.File)

Sun, 12 Nov 2006 15:17:00 GMT

import java.io.File;

public class MainClass {
     public static void main ( String args []) {
   File f1 = new File ( "MainClass.java" ) ;
   System.out.println ( "File Name:" + f1.getName ()) ;
   System.out.println ( "Path:" + f1.getPath ()) ;
   System.out.println ( "Abs Path:" + f1.getAbsolutePath ()) ;
   System.out.println ( "Parent:" + f1.getParent ()) ;
   System.out.println ( f1.exists () ? "exists" : "does not exist" ) ;
   System.out.println ( f1.canWrite () ? "is writeable" : "is not writeable" ) ;
   System.out.println ( f1.canRead () ? "is readable" : "is not readable" ) ;
   System.out.println ( "is a directory" + f1.isDirectory () ) ;
   System.out.println ( f1.isFile () ? "is normal file" : "might be a named pipe" ) ;
   System.out.println ( f1.isAbsolute () ? "is absolute" : "is not absolute" ) ;
   System.out.println ( "File last modified:" + f1.lastModified ()) ;
   System.out.println ( "File size:" + f1.length () + " Bytes" ) ;
     }
}

苑 2006-11-12 23:17 发表评论

java基础学习13(java.io.BufferedOutputStream)

Sun, 12 Nov 2006 15:14:00 GMT

import java.io.BufferedOutputStream;
import java.io.FileOutputStream;

public class MainClass {

   public static void main ( String args []) {

     try {

       FileOutputStream fos = new FileOutputStream ("fileName" ) ;

       BufferedOutputStream bos = new BufferedOutputStream ( fos ) ;

       for ( int i = 0 ; i < 12 ; i++ ) {
         bos.write ( i ) ;
       }

       bos.close () ;
     } catch ( Exception e ) {
       System.out.println ( "Exception: " + e ) ;
     }
   }
}

苑 2006-11-12 23:14 发表评论

java基础学习12(java.io.BufferedInputStream)

Sun, 12 Nov 2006 15:11:00 GMT

import java.io.BufferedInputStream;
import java.io.FileInputStream;

public class MainClass {

   public static void main ( String args []) {
     try {
       FileInputStream fis = new FileInputStream ("fileName" ) ;

       BufferedInputStream bis = new BufferedInputStream ( fis ) ;

       int i;
       while (( i = bis.read ()) != - 1 ) {
         System.out.println ( i ) ;
       }
       fis.close () ;
     } catch ( Exception e ) {
       System.out.println ( "Exception: " + e ) ;
     }
   }
}

苑 2006-11-12 23:11 发表评论

java基础学习11(java.util.Iterator)

Sun, 12 Nov 2006 15:07:00 GMT

import java.util.ArrayList;
import java.util.Iterator;
import java.util.ListIterator;

public class MainClass {
   public static void main ( String args []) {
     ArrayList al = new ArrayList () ;

     al.add ( "C" ) ;
     al.add ( "A" ) ;
     al.add ( "E" ) ;
     al.add ( "B" ) ;
     al.add ( "D" ) ;
     al.add ( "F" ) ;

     System.out.print ( "Original contents of al: " ) ;
     Iterator itr = al.iterator () ;
     while ( itr.hasNext ()) {
       String element = itr.next () ;
       System.out.print ( element + " " ) ;
     }
     System.out.println () ;

     ListIterator litr = al.listIterator () ;
     while ( litr.hasNext ()) {
       String element = litr.next () ;
       litr.set ( element + "+" ) ;
     }

     // Now, display the list backwards.
     System.out.print ( "Modified list backwards: " ) ;
     while ( litr.hasPrevious ()) {
       String element = litr.previous () ;
       System.out.print ( element + " " ) ;
     }
   }
}

苑 2006-11-12 23:07 发表评论

java基础学习10(java.util.properties)

Sun, 12 Nov 2006 15:03:00 GMT

import java.util.Properties;

public class MainClass {
     public static void main ( String args []) {
         Properties prop = new Properties () ;
         prop.put ( "a" , "1" ) ;
         prop.put ( "b" , "2" ) ;
         prop.put ( "c" , "3" ) ;
         Properties book = new Properties ( prop ) ;
         book.put ( "A" , "4" ) ;
         book.put ( "B" , "5" ) ;

         System.out.println ( "a " + book.getProperty ( "a" )) ;
         System.out.println ( "A " + book.getProperty ( "b" )) ;
         System.out.println ( "c: " + book.getProperty ( "c" )) ;

         System.out.println ( "z: " + book.getProperty ( "z" , "default" )) ;
     }
}

苑 2006-11-12 23:03 发表评论

java基础学习9(java.util.Vector)

Sun, 12 Nov 2006 15:02:00 GMT

import java.util.Vector;

public class MainClass {
   public static void main ( String args []) {

     // initial size is 3, increment is 2
     Vector v = new Vector ( 3 , 2 ) ;

     System.out.println ( "Initial size: " + v.size ()) ;
     System.out.println ( "Initial capacity: " + v.capacity ()) ;

     v.addElement ( 1 ) ;
     v.addElement ( 2 ) ;

     System.out.println ( "First element: " + v.firstElement ()) ;
     System.out.println ( "Last element: " + v.lastElement ()) ;

     if ( v.contains ( 3 ))
       System.out.println ( "Vector contains 3." ) ;
   }
}

苑 2006-11-12 23:02 发表评论

java基础学习8(java.util.Hashtable)

Sun, 05 Nov 2006 09:59:00 GMT

import java.util.Hashtable;
import java.util.Iterator;
import java.util.Set;

public class MainClass {
   public static void main ( String args []) {
     Hashtable balance = new Hashtable () ;

     String str;
     double bal;

     balance.put ( "A" , 4.34 ) ;
     balance.put ( "B" , 3.22 ) ;
     balance.put ( "C" , 8.00 ) ;
     balance.put ( "D" , 9.22 ) ;
     balance.put ( "E" , - 9.08 ) ;

     Set set = balance.keySet () ;

     Iterator itr = set.iterator () ;
     while ( itr.hasNext ()) {
       str = itr.next () ;
       System.out.println ( str + ": " + balance.get ( str )) ;
     }

     System.out.println () ;

     bal = balance.get ( "A" ) ;
     balance.put ( "A" , bal + 1000 ) ;
     System.out.println ( "A's new balance: " + balance.get ( "A" )) ;
   }
}

苑 2006-11-05 17:59 发表评论

java基础学习7(java.util.Enumeration)

Sun, 05 Nov 2006 09:57:00 GMT

import java.util.Enumeration;

class collection implements Enumeration {
   private int count = 0 ;

   private boolean more = true ;

   public boolean hasMoreElements () {
     return more;
   }

   public Object nextElement () {
     count++;
     if ( count > 4 )
       more = false ;
     return new Integer ( count ) ;
   }
}

public class MainClass {
   public static void main ( String args []) {
     Enumeration e = new collection () ;
     while ( e.hasMoreElements ()) {
       System.out.println ( e.nextElement ()) ;
     }
   }
}

苑 2006-11-05 17:57 发表评论

java基础学习6(java.util.Date)

Sun, 05 Nov 2006 09:56:00 GMT

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

public class MainClass {

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

     DateFormat df = new SimpleDateFormat ( "yyyy-MM-dd" ) ;

     Date d1 = df.parse ( "2001-01-01" ) ;

     Date d2 = df.parse ( "2000-01-01" ) ;

     String relation;
     if ( d1.equals ( d2 ))
       relation = "the same date as" ;
     else if ( d1.before ( d2 ))
       relation = "before" ;
     else if ( d1.after ( d2 ))
       relation = "after" ;
     System.out.println ( d1 + " is " + relation + ' ' + d2 ) ;
   }
}

苑 2006-11-05 17:56 发表评论

java基础学习5(java.util.Collections)

Sun, 05 Nov 2006 09:54:00 GMT

import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedList;

public class MainClass {
   public static void main ( String args []) {
     LinkedList ll = new LinkedList () ;
     ll.add ( - 8 ) ;
     ll.add ( 20 ) ;
     ll.add ( - 20 ) ;
     ll.add ( 8 ) ;

     Comparator r = Collections.reverseOrder () ;

     Collections.sort ( ll, r ) ;

     System.out.print ( "List sorted in reverse: " ) ;
     for ( int i : ll ){
       System.out.print ( i+ " " ) ;
     }

     System.out.println () ;

     Collections.shuffle ( ll ) ;

     System.out.print ( "List shuffled: " ) ;
     for ( int i : ll )
       System.out.print ( i + " " ) ;

     System.out.println () ;

     System.out.println ( "Minimum: " + Collections.min ( ll )) ;
     System.out.println ( "Maximum: " + Collections.max ( ll )) ;
   }
}

苑 2006-11-05 17:54 发表评论

java基础学习4(java.util.Calendar)

Sun, 05 Nov 2006 09:52:00 GMT

import java.util.Calendar;

public class MainClass {
   public static void main ( String args []) {
     String months [] = { "Jan" , "Feb" , "Mar" , "Apr" , "May" , "Jun" , "Jul" , "Aug" ,
         "Sep" , "Oct" , "Nov" , "Dec" } ;

     Calendar calendar = Calendar.getInstance () ;

     System.out.print ( "Date: " ) ;
     System.out.print ( months [ calendar.get ( Calendar.MONTH )]) ;
     System.out.print ( " " + calendar.get ( Calendar.DATE ) + " " ) ;
     System.out.println ( calendar.get ( Calendar.YEAR )) ;

     System.out.print ( "Time: " ) ;
     System.out.print ( calendar.get ( Calendar.HOUR ) + ":" ) ;
     System.out.print ( calendar.get ( Calendar.MINUTE ) + ":" ) ;
     System.out.println ( calendar.get ( Calendar.SECOND )) ;

     calendar.set ( Calendar.HOUR, 10 ) ;
     calendar.set ( Calendar.MINUTE, 29 ) ;
     calendar.set ( Calendar.SECOND, 22 ) ;

     System.out.print ( "Updated time: " ) ;
     System.out.print ( calendar.get ( Calendar.HOUR ) + ":" ) ;
     System.out.print ( calendar.get ( Calendar.MINUTE ) + ":" ) ;
     System.out.println ( calendar.get ( Calendar.SECOND )) ;
   }
}

苑 2006-11-05 17:52 发表评论

java基础学习2(java.util.ArrayList)

Sun, 05 Nov 2006 09:50:00 GMT

苑 2006-11-05 17:50 发表评论

java基础学习1(java.util.AbstractSet)

Sun, 05 Nov 2006 09:47:00 GMT

import java.io.Serializable;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.Set;

public class MainClass {
   public static void main ( String args []) {
     Set map = new ArraySet () ;
     map.add ( "V" ) ;
     map.add ( "M" ) ;
     map.add ( "N" ) ;
     System.out.println ( map ) ;
   }
}

class ArraySet extends AbstractSet implements Cloneable, Serializable {

   private ArrayList list;

   public ArraySet () {
     list = new ArrayList () ;
   }

   public ArraySet ( Collection col ) {
     list = new ArrayList () ;

     // No need to check for dups if col is a set
     Iterator itor = col.iterator () ;
     if ( col instanceof Set ) {
       while ( itor.hasNext ()) {
         list.add ( itor.next ()) ;
       }
     } else {
       while ( itor.hasNext ()) {
         add ( itor.next ()) ;
       }
     }
   }

   public Iterator iterator () {
     return list.iterator () ;
   }

   public int size () {
     return list.size () ;
   }

   public boolean add ( Object element ) {
     boolean modified;
     if ( modified = !list.contains ( element )) {
       list.add ( element ) ;
     }
     return modified;
   }

   public boolean remove ( Object element ) {
     return list.remove ( element ) ;
   }

   public boolean isEmpty () {
     return list.isEmpty () ;
   }

   public boolean contains ( Object element ) {
     return list.contains ( element ) ;
   }

   public void clear () {
     list.clear () ;
   }

   public Object clone () {
     try {
       ArraySet newSet = ( ArraySet ) super .clone () ;
       newSet.list = ( ArrayList ) list.clone () ;
       return newSet;
     } catch ( CloneNotSupportedException e ) {
       throw new InternalError () ;
     }
   }
}

苑 2006-11-05 17:47 发表评论

java基础学习3(java.util.Map)

Sun, 05 Nov 2006 09:44:00 GMT

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class MainClass {

   public static void main ( String [] argv ) {
     Map map = new HashMap () ;

     map.put ( "Adobe" , "Mountain View, CA" ) ;
     map.put ( "IBM" , "White Plains, NY" ) ;
     map.put ( "Learning Tree" , "Los Angeles, CA" ) ;

     Iterator k = map.keySet () .iterator () ;
     while ( k.hasNext ()) {
       String key = ( String ) k.next () ;
       System.out.println ( "Key " + key + "; Value " + ( String ) map.get ( key )) ;
     }
   }
}

苑 2006-11-05 17:44 发表评论