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‎javacollectionsframeworkexamples/JavaCollectionsFrameworkExamples.java

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package javacollectionsframeworkexamples;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.LinkedHashMap;
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import java.util.LinkedHashSet;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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import java.util.TreeMap;
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import java.util.TreeSet;
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/**
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*
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* @author Laszlo Harri Nemeth
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*/
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public class JavaCollectionsFrameworkExamples {
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/**
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* @param args the command line arguments
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*/
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public static void main(String[] args) {
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ArrayListVsLinkedList();
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HashMapLinkedHashMapTreeMapTest();
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SetsTest();
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}
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private static final void ArrayListVsLinkedList() {
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List<Integer> arrayList = new ArrayList();
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List<Integer> linkedList = new LinkedList();
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System.out.println("-------------------------------------------");
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System.out.println("Comparison of LinkedList and ArrayList performance");
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System.out.println("-------------------------------------------");
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doTimings("ArrayList", arrayList);
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doTimings("LinkedList", linkedList);
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System.out.println("-------------------------------------------");
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}
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private static void doTimings(String type, List<Integer> list) {
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for (int i = 0; i < 1E5; i++)
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list.add(i);
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long start = System.currentTimeMillis();
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// add items to the end of the list
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for (int i = 0; i < 1E5; i++)
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list.add(i);
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long end = System.currentTimeMillis();
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System.out.println("Time taken for adding items to the end: " + (end - start) + "ms for " + type);
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/* --------------------------------------------------------------*/
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list.clear();
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for (int i = 0; i < 1E5; i++)
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list.add(i);
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start = System.currentTimeMillis();
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// add items to the beginning of the list
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for (int i = 0; i < 1E5; i++)
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list.add(0, i);
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end = System.currentTimeMillis();
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System.out.println("Time taken for adding items to the beginning: " + (end - start) + "ms for " + type);
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/* --------------------------------------------------------------*/
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list.clear();
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for (int i = 0; i < 1E5; i++)
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list.add(i);
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start = System.currentTimeMillis();
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// add items to the beginning of the list
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for (int i = 0; i < 1E5; i++)
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list.add(list.size()-100, i);
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end = System.currentTimeMillis();
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System.out.println("Time taken for adding items near the end: " + (end - start) + "ms for " + type);
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}
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private static void HashMapLinkedHashMapTreeMapTest() {
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Map<Integer, String> hashMap = new HashMap<Integer, String>();
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Map<Integer, String> linkedHashMap = new LinkedHashMap<Integer, String>();
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Map<Integer, String> treeMap = new TreeMap<Integer, String>();
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// order not guaranteed
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System.out.println("-------------------------------------------");
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System.out.println("HashMap: order not guaranteed");
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testMap(hashMap);
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System.out.println("-------------------------------------------");
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System.out.println("LinkedHashMap: insertion order");
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testMap(linkedHashMap);
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System.out.println("-------------------------------------------");
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System.out.println("TreeMap: natural order");
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testMap(treeMap);
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System.out.println("-------------------------------------------");
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}
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private static void testMap(Map<Integer, String> map) {
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map.put(9, "Fox");
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map.put(4, "Cat");
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map.put(8, "Dog");
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map.put(1, "Giraffe");
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map.put(0, "Swan");
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map.put(15, "Bear");
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map.put(6, "Snake");
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for (Integer key : map.keySet()) {
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System.out.println(key + ": " + map.get(key));
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}
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}
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private static void SetsTest() {
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System.out.println("HashSet does not retain order");
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Set<String> set = new HashSet<String>();
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set.add("dog");
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set.add("cat");
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set.add("mouse");
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set.add("snake");
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set.add("bear");
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// add duplicate item doesn't add
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set.add("mouse");
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System.out.println(set);
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System.out.println("-------------------------------------------");
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System.out.println("LinkedHashSet remembers the order of insertion");
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Set<String> linkedHashSet = new LinkedHashSet<String>();
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linkedHashSet.add("dog");
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linkedHashSet.add("cat");
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linkedHashSet.add("mouse");
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linkedHashSet.add("snake");
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linkedHashSet.add("bear");
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// add duplicate item doesn't add
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linkedHashSet.add("mouse");
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System.out.println(linkedHashSet);
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System.out.println("-------------------------------------------");
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System.out.println("TreeSet sorts in natural order");
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Set<String> treeSet = new TreeSet<String>();
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treeSet.add("dog");
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treeSet.add("cat");
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treeSet.add("mouse");
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treeSet.add("snake");
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treeSet.add("bear");
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// add duplicate item doesn't add
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treeSet.add("mouse");
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System.out.println(treeSet);
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System.out.println("-------------------------------------------");
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System.out.println("Intersection:");
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Set<String> treeSet2 = new TreeSet<String>();
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// some common elements and some new elements
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treeSet2.add("dog");
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treeSet2.add("cat");
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treeSet2.add("giraffe");
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treeSet2.add("monkey");
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treeSet2.add("ant");
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System.out.println("Set1: " + treeSet);
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System.out.println("Set2: " + treeSet2);
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// copy treeSet
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Set<String> intersectionHashSet = new HashSet<String>(treeSet);
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// keep only the elements which are treeSet2 - therefore this will be the intersection
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intersectionHashSet.retainAll(treeSet2);
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System.out.println("Intersection: " + intersectionHashSet);
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System.out.println("-------------------------------------------");
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System.out.println("Difference:");
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System.out.println("Set1: " + treeSet);
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System.out.println("Set2: " + treeSet2);
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// copy treeSet
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Set<String> differenceHashSet = new HashSet<String>(treeSet);
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// remove all those elements which are in treeSet2. So the difference will be in differenceHashSet.
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differenceHashSet.removeAll(treeSet2);
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System.out.println("Difference (Set1 \\ Set2): " + differenceHashSet);
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System.out.println("-------------------------------------------");
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}
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}

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