JAVA基礎学習のMap集合,集合フレームワークツール類Collections,Arrays,可変パラメータ,List,Set集合フレームワークはいつ使用するかなど(4)
10028 ワード
package com.itcast.test20140113;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
public class MainDemo {
public static void main(String[] args) {
// Map
//MapUser();
/*
* , , class , ? 。 ?
* extends E E E 。 , ? super E
* E E 。 , public void printCollection(Collection<?
* extends Person> collection) public void
* printCollection(Collection<?> collection)
*/
//
CollectionUtilUser();
/*
* Arrays.toString(array);// toString[2,3,4]
*/
List<String> stooges = Arrays.asList("Larry", "Moe", "Curly");
System.out.println(stooges);// [Larry, Moe, Curly]
/*
* , ,
* ,
*/
int[] array = { 1, 3, 4 };
List<int[]> list = Arrays.asList(array);//
System.out.println(list);// [[I@4aa0b07b]
Integer [] array1 = { 1, 3, 4 };
List<Integer> integers = Arrays.asList(array1);//
System.out.println(integers);// [1, 3, 4]
Integer [] integers2 = integers.toArray(new Integer[integers.size()]);//
System.out.println(Arrays.toString(integers2));
//
// public static String Params(int... params){
// return Arrays.toString(params);
// }
// System.out.println(Params(1,2,3));//int... int[]
}
/**
*
*/
public static void CollectionUtilUser() {
/*
* Collections.sort(list);
* Collections.sort(list,CompareByStringLength); Comparator
* Collections.binarySearch(list, key)// , , , list key ,
* Collections.max(list);//
* Collections.reverse(list);//
* Collections.replaceAll(list, oldVal, newVal);
* Collections.shuffle(list);//
* Collections.synchronizedCollection(collection);
* Collections.synchronizedList(list);
* Collections.synchronizedMap(m);
* Collections.synchronizedSet(s);
*/
}
/**
* Map
*/
public static void MapUser() {
/*
* Map : value
* put(key,value) value, key , key, null void clear()
* value remove(key) boolean containsKey(key) boolean
* containsValue(value) boolean isEmpty() value
* get(key) , , null int size()
*/
/*
*
*/
Map<Integer, String> map = new HashMap<Integer, String>();
map.put(1, "a");
map.put(2, "b");
map.put(3, "c");
//
Set<Integer> set = map.keySet();
// Collection<String> collection = map.values();
for (Integer integer : set) {
System.out.println(integer + ":" + map.get(integer));
}
//
Set<Entry<Integer, String>> entrySet = map.entrySet();
for (Entry<Integer, String> entry : entrySet) {
System.out.println(entry.getKey() + ":" + entry.getValue());
}
/*
* Map : Hashtable: , , null ,null
* HashMap: , , null ,null 。
* TreeMap: , , Map
* HashMap LinkedHashMap:
*/
/*
* List Set
* :Set
* :TreeSet
* :LinkedHashSet
* : HashSet
* : List
* :LinkedList
* :ArrayList
*/
}
}