Merge pull request lokeshgupta1981#10 from ThakkarChandresh/master

Added : java cursors

Author: lokeshgupta1981

src/main/java/com/howtodoinjava/core/collections/cursors/AlternateNextAndPrevious.java

@@ -0,0 +1,28 @@
+package com.howtodoinjava.core.collections.cursors;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.ListIterator;
+
+public class AlternateNextAndPrevious {
+
+    public static void main(String[] args) {
+
+        List<Integer> numbers = new ArrayList<>();
+
+        for (int i = 1; i <= 5; i++) { numbers.add(i); }
+
+        ListIterator<Integer> iterator = numbers.listIterator();
+
+        System.out.println(iterator.next()); //1
+
+        System.out.println(iterator.next()); //2
+
+        System.out.println(iterator.previous()); //2
+
+        System.out.println(iterator.next()); //2
+
+        System.out.println(iterator.previous()); //2
+
+    }
+}

src/main/java/com/howtodoinjava/core/collections/cursors/ConcurrentModification.java

@@ -0,0 +1,36 @@
+package com.howtodoinjava.core.collections.cursors;
+
+import java.util.ArrayList;
+import java.util.ConcurrentModificationException;
+import java.util.List;
+import java.util.ListIterator;
+
+public class ConcurrentModification {
+
+    public static void main(String[] args) {
+
+        try {
+
+            List<Integer> numbers = new ArrayList<>();
+
+            for (int i = 1; i <= 5; i++) { numbers.add(i); }
+
+            ListIterator<Integer> iterator = numbers.listIterator();
+
+            System.out.println(iterator.next());
+
+            numbers.add(0, 10);
+
+            System.out.println(iterator.next());
+
+        } catch (ConcurrentModificationException exception) {
+
+            System.out.println("Attempted to the modify collection");
+
+            System.out.println(exception);
+
+        }
+
+    }
+
+}

src/main/java/com/howtodoinjava/core/collections/cursors/EnumerationCursor.java

@@ -0,0 +1,24 @@
+package com.howtodoinjava.core.collections.cursors;
+
+import java.util.Enumeration;
+import java.util.Vector;
+
+public class EnumerationCursor {
+
+    public static void main(String[] args) {
+
+        Vector<Integer> vector = new Vector<>();
+
+        for(int i=1;i<=10;i++){ vector.addElement(i); }
+
+        Enumeration<Integer> enumeration = vector.elements();
+
+        while(enumeration.hasMoreElements()){
+
+            System.out.print(enumeration.nextElement() + " ");
+
+        }
+
+    }
+
+}

src/main/java/com/howtodoinjava/core/collections/cursors/IteratorCursor.java

@@ -0,0 +1,27 @@
+package com.howtodoinjava.core.collections.cursors;
+
+import java.util.*;
+
+public class IteratorCursor {
+
+    public static void main(String[] args) {
+
+        Set<Integer> immutableSet = Set.of(1,2,3,4,5,6,7,8,9,10); // Immutable Set
+        Set<Integer> elements = new HashSet<>(immutableSet);  // Mutable Set
+
+        Iterator<Integer> iterator = elements.iterator();
+
+        int num;
+
+        while (iterator.hasNext()){
+
+            if ((num = iterator.next()) == 5){ iterator.remove(); }
+
+            else { System.out.print(num + " "); }
+        }
+
+        System.out.println("\n"+elements);
+
+    }
+
+}

src/main/java/com/howtodoinjava/core/collections/cursors/ListIteratorCursor.java

@@ -0,0 +1,48 @@
+package com.howtodoinjava.core.collections.cursors;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.ListIterator;
+
+public class ListIteratorCursor {
+
+    public static void main(String[] args) {
+
+        List<Integer> immutableList = List.of(1, 2, 3, 4, 5);
+        List<Integer> numbers = new ArrayList<>(immutableList);
+
+        ListIterator<Integer> iterator = numbers.listIterator();
+
+        int num;
+
+        while (iterator.hasNext()) {
+
+            num = iterator.next();
+
+            if (num == 1) { iterator.remove(); }
+
+            else if (num == 5){ iterator.set(50); }
+
+        }
+
+        iterator.add(6);
+
+        System.out.println(numbers);
+
+        while (iterator.hasPrevious()) {
+
+            num = iterator.previous();
+
+            if (num == 6) { iterator.remove(); }
+
+            else if (num == 50){ iterator.set(5);}
+
+        }
+
+        iterator.add(1);
+
+        System.out.println(numbers);
+
+    }
+
+}

src/main/java/com/howtodoinjava/core/collections/cursors/SpliteratorCursor.java

@@ -0,0 +1,29 @@
+package com.howtodoinjava.core.collections.cursors;
+
+import java.util.List;
+import java.util.Spliterator;
+import java.util.stream.Stream;
+
+public class SpliteratorCursor {
+
+    public static void main(String[] args) {
+
+        List<String> big = Stream.generate(() -> "Hello").limit(30000).toList();
+
+        Spliterator<String> split = big.spliterator(); // 30000
+
+        System.out.println(split.estimateSize());
+
+        Spliterator<String> split1 = split.trySplit();
+
+        System.out.println(split.estimateSize()); // 15000
+
+        System.out.println(split1.estimateSize()); // 15000
+
+        new Thread(() -> split.forEachRemaining(elem -> System.out.println("TH1 " + elem))).start();
+
+        new Thread(() -> split1.forEachRemaining(elem -> System.out.println("TH2 " + elem))).start();
+
+    }
+
+}

src/main/java/com/howtodoinjava/core/collections/cursors/SpliteratorEstimateSize.java

@@ -0,0 +1,25 @@
+package com.howtodoinjava.core.collections.cursors;
+
+import java.util.List;
+import java.util.Spliterator;
+import java.util.stream.Stream;
+
+public class SpliteratorEstimateSize {
+
+    public static void main(String[] args) {
+
+        List<String> big = Stream.generate(() -> "Hello").limit(10).toList();
+
+        Spliterator<String> split = big.spliterator();
+
+        split.tryAdvance(System.out::println);
+        split.tryAdvance(System.out::println);
+        split.tryAdvance(System.out::println);
+        split.tryAdvance(System.out::println);
+        split.tryAdvance(System.out::println);
+
+        System.out.println(split.estimateSize());
+
+    }
+
+}