collection iteration basics

Author: Ram swaroop

src/me/ramswaroop/misc/CollectionIteration.java

@@ -0,0 +1,50 @@
+package me.ramswaroop.misc;
+
+import java.util.*;
+
+import static java.lang.System.out;
+
+/**
+ * Created by IntelliJ IDEA.
+ * <p/>
+ * All possible ways of iterating different collections in Java.
+ *
+ * @author: ramswaroop
+ * @date: 10/16/15
+ * @time: 9:24 AM
+ */
+public class CollectionIteration {
+
+    public static void main(String a[]) {
+        List<Integer> list = new ArrayList<>();
+        list.add(1);
+        list.add(2);
+        list.add(3);
+        // 1st way
+        Iterator<Integer> iterator = list.iterator();
+        while (iterator.hasNext()) {
+            out.println("List: " + iterator.next());
+        }
+        // 2nd way
+        for (int i = 0; i < list.size(); i++) {
+            out.println("List: " + list.get(i));
+        }
+
+        Map<String, Integer> hashMap = new HashMap<>();
+        hashMap.put("one", 1);
+        hashMap.put("two", 2);
+        hashMap.put("three", 3);
+        // 1st way
+        Iterator<Map.Entry<String, Integer>> iterator1 = hashMap.entrySet().iterator(); // iterator only iterates on 
+                                                                                        // lists or set and not on maps
+        while (iterator1.hasNext()) {
+            Map.Entry<String, Integer> entry = iterator1.next();
+            out.println("HashMap: " + entry.getKey() + "->" + entry.getValue());
+        }
+        // 2nd way
+        for (Map.Entry<String, Integer> entry : hashMap.entrySet()) {   // entrySet() returns a Set of Entry objects 
+                                                                        // stored in HashMap
+            out.println("HashMap: " + entry.getKey() + "->" + entry.getValue());
+        }
+    }
+}