java中的泛型 (一)

import java.util.Set;

//dao data access object--->crud
public class GenericDao  {
 public void add(E x){
  
 }
 
 public E findById(int id){
  return null;
 }
 
 public void delete(E obj){
  
 }
 
 public void delete(int id){
  
 } 
 
 public void update(E obj){
  
 }
 
 public static  void update2(E obj){
  
 }
 
 public E findByUserName(String name){
  return null;
 }
 public Set findByConditions(String where){
  return null;
 }
}


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import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.Vector;

import cn.itcast.day1.ReflectPoint;

public class GenericTest {

 /**
  * @param args
  */
 public static void main(String[] args) throws Exception {
  // TODO Auto-generated method stub
  ArrayList collection1 = new ArrayList();
  collection1.add(1);
  collection1.add(1L);
  collection1.add("abc");
  //int i = (Integer)collection1.get(1);
  
  ArrayList collection2 = new ArrayList();
  //collection2.add(1);
  //collection2.add(1L);
  collection2.add("abc");
  String element = collection2.get(0); 
  
  //new String(new StringBuffer("abc"));
  Constructor constructor1 = String.class.getConstructor(StringBuffer.class);
  String str2 = constructor1.newInstance(/*"abc"*/new StringBuffer("abc"));
  System.out.println(str2.charAt(2));  
  
  ArrayList collection3 = new ArrayList();
  System.out.println(collection3.getClass() == collection2.getClass());
  //collection3.add("abc");
  collection3.getClass().getMethod("add", Object.class).invoke(collection3, "abc");
  System.out.println(collection3.get(0));
  
  printCollection(collection3);
  
  //Class





 x = String.class.asSubclass(Number.class);
  Class< > y;
  Class x ;//Class.forName("java.lang.String");
  
  HashMap maps = new HashMap();
  maps.put("zxx", 28);
  maps.put("lhm", 35);
  maps.put("flx", 33);
  
  Set> entrySet = maps.entrySet();
  for(Map.Entry entry : entrySet){
   System.out.println(entry.getKey() + ":" + entry.getValue());
  }
  
  add(3,5);
  Number x1 = add(3.5,3);
  Object x2 = add(3,"abc");
  
  swap(new String[]{"abc","xyz","itcast"},1,2);
  //swap(new int[]{1,3,5,4,5},3,4);
  
  Object obj = "abc";
  String x3 = autoConvert(obj);
  
  copy1(new Vector(),new String[10]);
  copy2(new Date[10],new String[10]);  
  //copy1(new Vector(),new String[10]);
  
  GenericDao dao = new GenericDao();
  dao.add(new ReflectPoint(3,3));  
  //String s = dao.findById(1);
  
  //Vector v1 = new Vector();
  Method applyMethod = GenericTest.class.getMethod("applyVector", Vector.class);
  Type[] types = applyMethod.getGenericParameterTypes();
  ParameterizedType pType = (ParameterizedType)types[0];
  System.out.println(pType.getRawType());
  System.out.println(pType.getActualTypeArguments()[0]);
 }
 
 public static void applyVector(Vector v1){
  
 }

 
 private static  void fillArray(T[] a,T obj){
  for(int i=0;i T autoConvert(Object obj){
  return (T)obj;
 }
 private static  void swap(T[] a,int i,int j){
  T tmp = a[i];
  a[i] = a