~~~ package arraylist.a4; import java.util.*; public class Test { public static void main(String[] args) throws Exception{ HashMap ee=new HashMap(); Sp sp1=new Sp("001","話梅",5f); Sp sp2=new Sp("002","薯片",8f); ee.put("001", sp1); ee.put("002", sp2);//鍵 值 if(ee.containsKey("002")){//不需要遍歷 System.out.println("該食品的信息為："); Sp sp=(Sp)ee.get("002"); System.out.println(sp.getMingcheng()); System.out.println(sp.getJiage()); }else{ System.out.println("對不起，沒有該食品"); } } } class Sp{ private String bianhao; private String mingcheng; private float jiage; public Sp(String bianhao, String mingcheng, float jiage) { super(); this.bianhao = bianhao; this.mingcheng = mingcheng; this.jiage = jiage; } public String getBianhao() { return bianhao; } public void setBianhao(String bianhao) { this.bianhao = bianhao; } public String getMingcheng() { return mingcheng; } public void setMingcheng(String mingcheng) { this.mingcheng = mingcheng; } public float getJiage() { return jiage; } public void setJiage(float jiage) { this.jiage = jiage; } } ~~~  HashMap的遍歷 ~~~ package arraylist.a4; import java.util.*; public class Test { public static void main(String[] args) throws Exception{ HashMap ee=new HashMap(); Sp sp1=new Sp("001","話梅",5f); Sp sp2=new Sp("002","薯片",8f); ee.put("001", sp1); ee.put("002", sp2);//鍵 值 /*if(ee.containsKey("002")){//不需要遍歷 System.out.println("該食品的信息為："); Sp sp=(Sp)ee.get("002"); System.out.println(sp.getMingcheng()); System.out.println(sp.getJiage()); }else{ System.out.println("對不起，沒有該食品"); }*/ //遍歷 Iterator it =ee.keySet().iterator();//所有的鍵值都激活，都給取出來 while(it.hasNext()){//還有沒有下一個，有為真，沒有為假 String key=it.next().toString(); Sp sp=(Sp)ee.get(key); System.out.println("食品名稱："+sp.getMingcheng()); System.out.println("食品價格："+sp.getJiage()+"元"); } } } class Sp{ private String bianhao; private String mingcheng; private float jiage; public Sp(String bianhao, String mingcheng, float jiage) { super(); this.bianhao = bianhao; this.mingcheng = mingcheng; this.jiage = jiage; } public String getBianhao() { return bianhao; } public void setBianhao(String bianhao) { this.bianhao = bianhao; } public String getMingcheng() { return mingcheng; } public void setMingcheng(String mingcheng) { this.mingcheng = mingcheng; } public float getJiage() { return jiage; } public void setJiage(float jiage) { this.jiage = jiage; } } ~~~