How to use different types of Collections in Java

Problem Description

How to use different types of Collections?

Solution

Following example uses different types of collection classes and adds an element in those collections.

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();
   }
}

Result

The above code sample will produce the following result.

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