HashMap 不会重复的Arrays

package coins;import java.util.HashMap;import java.util.Scanner;public class Coin {private HashMap<Integer,String> coinnames = new HashMap<Integer,String>();public Coin(){coinnames.put(1,"penny");coinnames.put(10,"dime");coinnames.put(25,"quarter");coinnames.put(50,"half_dolar");coinnames.put(50, "五毛");System.out.println(coinnames.keySet().size());//得到HashMap数量System.out.println(coinnames);//打印HashMapfor(Integer k : coinnames.keySet() ) {String s = coinnames.get(k);System.out.println(s);}}public String getName(int amount){if(coinnames.containsKey(amount))return coinnames.get(amount);elsereturn "Not Found";}public static void main(String[] args) {Scanner in =new Scanner(System.in);int amount = in.nextInt();Coin coin = new Coin();String name = coin.getName(amount);System.out.println(name);}}

新加进去的同名东西会覆盖掉以前的东西，用foreach可以遍历里面每一个数据

HashMap 一对一对的值，一个索引，一个值