Java 实例 - 集合中添加不同类型元素

以下实例演示了在集合类中添加不同类型的元素：

Main.java 文件 import java.util.Map; import java.util.Set; import java.util.SortedMap; import java.util.SortedSet; import java.util.TreeMap; import java.util.TreeSet;

import java.util.ArrayList; import java.util.Collection; import java.util.HashMap; import java.util.HashSet; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.LinkedHashSet; import java.util.LinkedList; import java.util.List;

public class Main { public static void main(String[] args) { List lnkLst = new LinkedList(); lnkLst.add("element1"); lnkLst.add("element2"); lnkLst.add("element3"); lnkLst.add("element4"); displayAll(lnkLst); List aryLst = new ArrayList(); aryLst.add("x"); aryLst.add("y"); aryLst.add("z"); aryLst.add("w"); displayAll(aryLst); Set hashSet = new HashSet(); hashSet.add("set1"); hashSet.add("set2"); hashSet.add("set3"); hashSet.add("set4"); displayAll(hashSet); SortedSet treeSet = new TreeSet(); treeSet.add("1"); treeSet.add("2"); treeSet.add("3"); treeSet.add("4"); displayAll(treeSet); LinkedHashSet lnkHashset = new LinkedHashSet(); lnkHashset.add("one"); lnkHashset.add("two"); lnkHashset.add("three"); lnkHashset.add("four"); displayAll(lnkHashset); Map map1 = new HashMap(); map1.put("key1", "J"); map1.put("key2", "K"); map1.put("key3", "L"); map1.put("key4", "M"); displayAll(map1.keySet()); displayAll(map1.values()); SortedMap map2 = new TreeMap(); map2.put("key1", "JJ"); map2.put("key2", "KK"); map2.put("key3", "LL"); map2.put("key4", "MM"); displayAll(map2.keySet()); displayAll(map2.values()); LinkedHashMap map3 = new LinkedHashMap(); map3.put("key1", "JJJ"); map3.put("key2", "KKK"); map3.put("key3", "LLL"); map3.put("key4", "MMM"); displayAll(map3.keySet()); displayAll(map3.values()); } static void displayAll(Collection col) { Iterator itr = col.iterator(); while (itr.hasNext()) { String str = (String) itr.next(); System.out.print(str + " "); } System.out.println(); } }

以上代码运行输出结果为：

element1 element2 element3 element4 
x y z w 
set3 set2 set4 set1 
1 2 3 4 
one two three four 
key1 key2 key3 key4 
J K L M 
key1 key2 key3 key4 
JJ KK LL MM 
key1 key2 key3 key4 
JJJ KKK LLL MMM