David's Untitled Life

public   class  Artist   {
    
    String[] others;
     /** */ /**  Creates a new instance of Artist  */ 
      public  Artist()   {
    } 
      public  Artist(String name,String ... others)  {
         for (String other : others)  {
            System.out.println(other);
        } 
         this .others  =  others;
    } 
      public   void  wildestMethod(Object ... objs)  {
     // this method will accept any arguments 
     } 
      public   static   void  main(String[] args)  {
        Artist artist  =   new  Artist( " You " ,  " 1 " ,  " 2 " );
        artist.wildestMethod( 1 ,  3.5 ,  " AA " ,  new  Artist());
    } 
    
}

public class AutoBoxing {
    
    /** Creates a new instance of AutoBoxing */
    public AutoBoxing() {
    }
    public void boxingDemo(){
        //auto boxing
        Integer i = 0;
        float f = 1.66f;
        Float F = f;
        //auto unboxing
        Integer I = new Integer(1);
        int i2 = I;
        //null value test, it will case NullPointerException
        Integer I2 = null;
        int i3 = I2;
    }
    public void testOperator(){
        Integer i = 1;
        while(true){
            i++;
            System.out.println("Counter:"+i);
            if(i>5) break;
        }
    }
    public void testCompare(){
        //it's equal because -127~127 are immutable objects
        Integer i = 1;
        Integer i2 = 1;
        if(i == i2) System.out.println("1:Equal");
        else System.out.println("1:Not Equal");
        //it's not equal because j and j2 are different objects
        Integer j = 200;
        Integer j2 =200;
        if(j == j2) System.out.println("200:Equal");
        else System.out.println("200:Not Equal");
    }
    public void testControl(){
        Boolean flag = true;
        Integer i = 20;
        Integer j = 30;
        if(flag){
            System.out.println("Boolean affects");
        }
        if(i<j)
            System.out.println("Integer affects");
    }
    public void testMethod(double arg){
        System.out.println("public void testMethod(double arg) is invoked");
    }
    public void testMethod(Integer arg){
        System.out.println("public void testMethod2(Integer arg) is invoked");
    }
    public static void main(String args[]){
        AutoBoxing auto = new AutoBoxing();
        auto.testCompare();
        auto.testOperator();
        auto.testControl();
        int i = 1;
        // public void testMethod(Integer arg) wouldn't be invoked
        //because  public void testMethod(double arg) will be invoked in JDK1.4
        //Java tiger consider the backward capability
        auto.testMethod(i);
        auto.boxingDemo();
    }
    
}

public enum User {
    Admin,User,Guest,Unknown   
}

public class Login {
    
    private User user;
    EnumMap<User,String> userName = new EnumMap<User, String>(User.class);
    /** Creates a new instance of Login */
    public Login() {
        userName.put(User.Admin, "Administrator");
        userName.put(User.User, "David");
        userName.put(User.Guest, "Steve");
    }
    public boolean isAdmin(User user){
        if(user.equals(User.Admin)){
            return true;
        }
        return false;
    }
    public void printUserRole(){
        User[] users = user.values();
        for(User u : user.values()){
            System.out.println(u.toString());
        }
    }
    public void isRole(User user){
        switch(user){
            case Admin:
                System.out.println("admin");
                break;
            case User:
                System.out.println("User");
                break;
            case Guest:
                System.out.println("Guest");
                break;
            default:
                System.out.println("unknow");
        }
    }
    public static void main(String[] args){
        Login login = new Login();
        System.out.println(login.isAdmin(User.Admin));
        login.printUserRole();
        login.isRole(User.User);
    }
    
}

/**
 * public class Box<T extends Number>
 * @author david.duan
 */
public class Box<T> {
    
    //you can't have a static variable such as protected static List<T> list...
    protected List<T> contents;
    
    public Box( ) {
        contents = new ArrayList<T>( );
    }
    public int getSize( ) {
        return contents.size( );
    }
    public boolean isEmpty( ) {
        return (contents.size( ) == 0);
    }
    public void add(T o) {
        contents.add(o);
    }
    public T grab( ) {
        if (!isEmpty( )) {
            return contents.remove(0);
        } else
            return null;
    }
    public static void main(String[] args){
        Box<String> box = new Box<String>();
        //...
    }
}

public class Generic {
    
    /** Creates a new instance of Generic */
    public Generic() {
    }
    
    public void collectionGeneric(){
        //generic list
        List<String> onlyStrings = new LinkedList<String>();
        onlyStrings.add("Legal addition");
        //generic map
        Map<Integer, Integer> squares = new HashMap<Integer, Integer>();
        for (int i=0; i<100; i++) {
            squares.put(i, i*i);
        }
        for (int i=0; i<10; i++) {
            int n = i*3;
            System.out.println("The square of " + n + " is " + squares.get(n));
        }
        //generic iterator
        List<String> listOfStrings = new LinkedList<String>();
        listOfStrings.add("Happy");
        listOfStrings.add("Birthday");
        for (Iterator<String> i = listOfStrings.iterator(); i.hasNext( ); ) {
            String s = i.next( );
            System.out.println(s);
        }
    }
    //parameter generic
    public void paramGeneric(List<String> list){
        for(Iterator<String> i = list.iterator();i.hasNext();){
            String s = i.next();
            System.out.println(s);
        }
    }
    //return generic
    public List<String> returnGeneric(){
        List<String> list = new LinkedList<String>();
        list.add("string1");
        return list;
    }
    //conversion
    public void conversionGeneric(){
        LinkedList<Float> floatList = new LinkedList<Float>();
        List<Float> moreFloats = floatList;
        //illegal conversion LinkedList<Number> numberList = floatList;
        //the way to resolve for backward capbility
        List<Integer> ints = new LinkedList<Integer>();
        List oldList = ints;
        List<Number> numList = oldList;
    }
    //generic wildcard : this old plain way will generate unchecked warning
    public void wildcardGeneric(List list){
        for (Iterator i = list.iterator(); i.hasNext(); ) {
            System.out.println(i.next().toString());
        }
    }
    //generic wildcard
    public void wildcardGeneric2(List<?> list){
        //you can't solve the problem by List<Object>
        for (Iterator<?> i = list.iterator( ); i.hasNext(); ) {
            System.out.println(i.next().toString( ));
        }
    }
    
}

 int[][] ar = {{1,2,3},{4,5,6}};
        int[][] br = {{1,2,3},{4,5,6}};
        System.out.println(Arrays.deepToString(ar));
        System.out.println(Arrays.deepEquals(ar,br));
        StringBuilder sb = new StringBuilder("string builder");

BIRT is really a amazing report tool. It's so powerful and free.
No more crap, just check this flash demo http://download.eclipse.org/birt/downloads/examples/misc/BIRT/BIRT_demo_Camv3.html

I uploaded a document about SAP and JAVA's intergration.
It introduce BAPI RFC ALE IDoc JCo's basic concept. Enjoy it.
http://blueoxygen.dflying.net/3/resources/Java_SAP_Integration.pdf.html

Recently,SUN publish Netbeans new release.Because project's requirement,I should use netbeans to design Swing UI. And at first,i really thought Netbeans Swing UI design tools pretty cool. But then i know,that's a vendor's production.Tody i got news from TheServerSide that the compony which design the Swing tools for SUN is supporting MyEclipse and i tried that.As convenience as it performed on NetBeans platform.
You can get a quic start here.Good luck.

Now the last reason to use NetBeans has gone.BTW,NetBeans default keymap really sucks!!! Ctrl+S means Search by default.The Netbeans designers are crazy??

Hibernate and Lazy Initialization

Hibernate object relational mapping offers both lazy and non-lazy modes of object initialization. Non-lazy initialization retrieves an object and all of its related objects at load time. This can result in hundreds if not thousands of select statements when retrieving one entity. The problem is compounded when bi-directional relationships are used, often causing entire databases to be loaded during the initial request. Of course one could tediously examine each object relationship and manually remove those most costly, but in the end, we may be losing the ease of use benefit sought in using the ORM tool.

The obvious solution is to employ the lazy loading mechanism provided by hibernate. This initialization strategy only loads an object's one-to-many and many-to-many relationships when these fields are accessed. The scenario is practically transparent to the developer and a minimum amount of database requests are made, resulting in major performance gains. One drawback to this technique is that lazy loading requires the Hibernate session to remain open while the data object is in use. This causes a major problem when trying to abstract the persistence layer via the Data Access Object pattern. In order to fully abstract the persistence mechanism, all database logic, including opening and closing sessions, must not be performed in the application layer. Most often, this logic is concealed behind the DAO implementation classes which implement interface stubs. The quick and dirty solution is to forget the DAO pattern and include database connection logic in the application layer. This works for small applications but in large systems this can prove to be a major design flaw, hindering application extensibility.

POJO used by Hibernate needs to implement hashCode() and equals() method.That's a kind of stuffy work and will be done many many times during development.Some IDEs support automatical generation feature such as IDEA.Eclipse famous plug-in--MyElipse also suppots but it's not free of charge.
I think nearly all JAVAers know Apache Commons open source project.We can use Commons lib to generate hashCode() and equals() method.I wanna tell you that there is also a plugin for Eclipse called Commons4E which help you generate hasCode() and equals().
It also can generate toString() and compareTo() method.That's a smart plugin.Enjoy it.Link