我们想要在同一个集合中放入不同的数据类型，请看如下代码

完整代码

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("num1");lnkLst.add("num2");lnkLst.add("num3");lnkLst.add("num4");displayAll(lnkLst);List aryLst = new ArrayList();aryLst.add("h");aryLst.add("a");aryLst.add("n");aryLst.add("g");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", "ab");map2.put("key2", "cd");map2.put("key3", "ef");map2.put("key4", "gh");displayAll(map2.keySet());displayAll(map2.values());LinkedHashMap map3 = new LinkedHashMap();map3.put("key1", "aaa");map3.put("key2", "bbb");map3.put("key3", "ccc");map3.put("key4", "ddd");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();}
}

结果输出

num1 num2 num3 num4
h  a  n  g
set3 set2 set4 set1 
1 2 3 4 
one two three four 
key1 key2 key3 key4 
J K L M 
key1 key2 key3 key4 ab   cd   ef   gh
key1 key2 key3 key4 
aaa   bbb ccc  ddd