JDK5.0的11个主要新特征

ArrayList<Integer> listOfIntegers; // <TYPE_NAME> is new to the syntax

Integer integerObject;

listOfIntegers = new ArrayList<Integer>(); // <TYPE_NAME> is new to the syntax

listOfIntegers.add(new Integer(10)); // 只能是Integer类型

integerObject = listOfIntegers.get(0); // 取出对象不需要转换 

HashMap<String,Float> hm = new HashMap<String,Float>();

//不能使用原始类型

GenList<int> nList = new GenList<int>();  //编译错误 

public interface GenInterface<T> {

    void func(T t);

} 

public class ArrayList<ItemType> { ... }

public class GenMap<T, V> { ... }

例1：

public class MyList<Element> extends LinkedList<Element>

{

       public void swap(int i, int j)

       {

              Element temp = this.get(i);

              this.set(i, this.get(j));

              this.set(j, temp);

       }

       public static void main(String[] args)

       {

              MyList<String> list = new MyList<String>();

              list.add("hi");

              list.add("andy");

              System.out.println(list.get(0) + " " + list.get(1));

              list.swap(0,1);

              System.out.println(list.get(0) + " " + list.get(1));

       }

} 

public class GenList <T>{

       private T[] elements;

       private int size = 0;

       private int length = 0;

       public GenList(int size) {

              elements = (T[])new Object[size];

              this.size = size;

       }

       public T get(int i) {

              if (i < length) {

                     return elements[i];

              }

              return null;

       }

       public void add(T e) {

              if (length < size - 1)

                     elements[length++] = e;

       }

} 

public class TestGenerics{

       public <T> String getString(T obj) { //实现了一个泛型方法

              return obj.toString();

       }

       public static void main(String [] args){

              TestGenerics t = new TestGenerics();

              String s = "Hello";

              Integer i = 100;

              System.out.println(t.getString(s));

              System.out.println(t.getString(i));

              }

}