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# Java Examples - Use Collections

## 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 ma p1 = 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

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