package javaee.china.cxp;
 
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
 
import org.junit.Test;
/**
 * 增强for循环
 * jdk1.5以上才能支持
 * 增加for循环只能用在数组或实现Iterable接口的集合上
 * 增加for只适合取数据
 */
public class Demo_5_for {

 
 
 @Test
 public void demo5_1(){
  /**
   * 增强for循环 数组实验
   */
  int[] arr = {1,2,3,4,5,6,7};
  for (int i:arr) {
   System.out.println(i);
  }
 }
 
 /**
  * 增强for循环 数组赋值实验
  * 证明增强for循环 无法赋值 只适合取数据
  * 如果要赋值请使用传统的For循环
  */
 @Test
 public void demo5_1_1(){
  int[] arr = {1,2,3,4,5,6,7};
  for (int i:arr) {
   arr[i] = 10;//i为对象 无法当整醒数组
  }
  for(int i:arr){
   System.out.println(i);
  }
 }
 
 /**
  * 展示HashMap传统的存取方法一
  */
 @Test
 public void demo5_2(){
  Map map = new HashMap();
  map.put("1", "a");
  map.put("2", "b");
  map.put("3", "c");
  map.put("4", "d");
  
  Set set = map.keySet();
  Iterator it = set.iterator();
  while(it.hasNext()){
   String key = (String) it.next();
   String value = (String) map.get(key);
   System.out.println(key+":"+value);
  }
 }
 
 /**
  * LinkedHashMap线性存储实验
  * 个人认为LinkedHashMap 比 HashMap 更容易使用 因为存储顺序一样
  */
 @Test
 public void demo5_3(){
  Map map = new LinkedHashMap();//LinkedHashMap属于线性列表  存取顺序一样
  map.put("1", "a");
  map.put("2", "b");
  map.put("3", "c");
  map.put("4", "d");
  
  Set set = map.keySet();
  Iterator it = set.iterator();
  while(it.hasNext()){
   String key = (String) it.next();
   String value = (String) map.get(key);
   System.out.println(key+":"+value);
  }
 }
 
 /**
  * 展示HashMap传统的存取方法二
  */
 @Test
 public void demo5_4(){
  Map map = new HashMap();
  map.put("1", "a");
  map.put("2", "b");
  map.put("3", "c");
  map.put("4", "d");
  
  Set set = map.entrySet();
  Iterator it = set.iterator();
  while(it.hasNext()){
   Map.Entry entry = (Entry) it.next();
   String key = (String) entry.getKey();
   String value = (String) entry.getValue();
   System.out.println(key+":"+value);
  }
 }
 
 /**
  * 增强for循环 HashMap实验
  * HashMap并没有实现Iterable接口 变相将其转换实现Iterable接口
  * 展示HashMap传统的存取方法一
  */
 @Test
 public void demo5_5(){
  Map map = new HashMap();
  map.put("1", "a");
  map.put("2", "b");
  map.put("3", "c");
  map.put("4", "d");
  
  Set set = map.keySet();
  for(Object j:set){
   String key = (String)j;
   String value = (String) map.get(key);
   System.out.println(key+":"+value);
  }
/*  while(it.hasNext()){
   String key = (String) it.next();
   String value = (String) map.get(key);
   System.out.println(key+":"+value);
  }*/
 }
 
 /**
  * 增强for循环 HashMap实验
  * HashMap并没有实现Iterable接口 变相将其转换实现Iterable接口
  * 展示HashMap传统的存取方法二
  */
 @Test
 public void demo5_6(){
  Map map = new HashMap();
  map.put("1", "a");
  map.put("2", "b");
  map.put("3", "c");
  map.put("4", "d");
  
  Set set = map.entrySet();
  for(Object j:set){
   Entry entry = (Entry) j;
   String key = (String) entry.getKey();
   String value = (String) entry.getValue();
   System.out.println(key+":"+value);
  }
 }
 
}