package com.crow;

/**

* Created by CrowHawk on 17/2/16.

*/

import java.lang.reflect.Method;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

public class GenericTest {

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

HashMap<String, Integer> hashMap = new HashMap<String, Integer>();

hashMap.put("Tom", 1);

hashMap.put("Jerry", 2);

hashMap.put("Nick", 3);

printHashmap(hashMap);

String[] array = new String[]{"crow","martin","pattie"};

swap(array, 1, 2);

System.out.println("array[2] = " + array[2]);

//用反射的方法获取printHashmap方法的参数并打印

Method printMethod = GenericTest.class.getMethod("printHashmap", HashMap.class);

Type[] types = printMethod.getGenericParameterTypes();

ParameterizedType parameterizedType = (ParameterizedType)types[0];

Type[] actualTypes = parameterizedType.getActualTypeArguments();

System.out.println("The paratype is " + parameterizedType.getRawType() + "<" + actualTypes[0] + "," + actualTypes[1] + ">");

}

public static void printHashmap(HashMap<String, Integer> hashMap){//遍历HashMap并打印其内容

Set<Map.Entry<String, Integer>> entrySet = hashMap.entrySet();

for(Map.Entry<String, Integer> entry: entrySet){

System.out.println(entry.getKey() + "," + entry.getValue());

}

Iterator<Map.Entry<String, Integer>> iter = entrySet.iterator();

while(iter.hasNext()){

Map.Entry<String, Integer> entry = iter.next();

System.out.print("Key is " + entry.getKey() + ",");

System.out.println("Value is " + entry.getValue());

}

}

public static <T> void swap(T[] arr, int i, int j){//交换泛型数组中的任意两个元素

T tmp = arr[i];

arr[i] = arr[j];

arr[j] = tmp;

}

}