Add blopost example for the removeIf, removeAll and isEmpty method of the arrayList in java

Author: gauravkukade

collections/arraylist/arraylist-isempty-method/ArrayListIsEmptyExample.java

@@ -0,0 +1,44 @@
+package com.gaurav.ExProject.ArrayList;
+
+import java.util.ArrayList;
+/**
+ * An example java program for an isEmpty method 
+ * of the ArrayList class in java.
+ * 
+ * @author Gaurav Kukade at coderolls
+ */
+public class ArrayListIsEmptyExample {
+
+	public static void main(String[] args) {
+		
+		// create an arraylyst teams
+		ArrayList<String> teams = new ArrayList<String>();
+		
+		// add elements to the arraylist teams
+		teams.add("LA Galaxy");
+		teams.add("Orlando City FC");
+		teams.add("Portland Timbers");
+		teams.add("Columbus Crew");
+		
+		boolean isTeamsEmpty = teams.isEmpty();
+		
+		if(isTeamsEmpty) {
+			System.out.println("Teams arraylist is empty.");
+		}
+		else {
+			System.out.println("Teams arraylist is not empty.");
+		}
+		
+		// create an arraylist players
+		ArrayList<String> players = new ArrayList<String>();
+		
+		boolean isPlayersEmpty = players.isEmpty();
+		
+		if(isPlayersEmpty) {
+			System.out.println("Players arraylist is empty.");
+		}
+		else {
+			System.out.println("Players arraylist is not empty.");
+		}
+	}
+}

collections/arraylist/arraylist-removeall-method/ArrayListRemoveAllExample.java

@@ -0,0 +1,49 @@
+package com.gaurav.ExProject.ArrayList;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Predicate;
+
+/**
+ * A java program showing an example for the removeAll()
+ * method of the ArrayList class in Java.
+ * 
+ * @author gaurav
+ */
+public class ArrayListRemoveAllExample {
+
+	public static void main(String[] args) {
+
+		// create an empty arraylist object 'states'
+		List<String> states = new ArrayList<String>();
+
+		// add state in the arraylist, Florida multiple times
+		states.add("California");
+		states.add("Texas");
+		states.add("Montana");
+		states.add("Arizona");
+		states.add("Florida");
+		states.add("Michigan");
+		states.add("New Jersey");
+		states.add("Washington");
+		states.add("Ohio");
+		states.add("Minnesota");
+		states.add("Colorado");
+		states.add("Missouri");
+		states.add("Nevada");		
+		
+		// create another ArrayList for items to be removed
+		List<String> statesToBeRemoved = new ArrayList<String>();
+		statesToBeRemoved.add("Minnesota");
+		statesToBeRemoved.add("Missouri");
+		statesToBeRemoved.add("Montana");
+		statesToBeRemoved.add("Michigan");
+		
+		System.out.println("The states list before the removeAll() method call: \n" + states);
+		
+		// removes all elements specified in the ArrayList statesToBeRemoved 
+		states.removeAll(statesToBeRemoved); 
+		
+		System.out.println("\nThe states list after the removeAll() method call: \n" + states);
+	}
+}

collections/arraylist/arraylist-removeall-method/ArrayListRemoveAllNullPointerException.java

@@ -0,0 +1,46 @@
+package com.gaurav.ExProject.ArrayList;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Predicate;
+
+/**
+ * A java program showing a NullPointerException case 
+ * for the removeAll() method of the ArrayList class in Java.
+ * 
+ * @author gaurav
+ */
+public class ArrayListRemoveAllNullPointerException {
+
+	public static void main(String[] args) {
+
+		// create an empty arraylist object 'states'
+		List<String> states = new ArrayList<String>();
+
+		// add state in the arraylist, Florida multiple times
+		states.add("California");
+		states.add("Texas");
+		states.add("Montana");
+		states.add("Arizona");
+		states.add("Florida");
+		states.add("Michigan");
+		states.add("New Jersey");
+		states.add("Washington");
+		states.add("Ohio");
+		states.add("Minnesota");
+		states.add("Colorado");
+		states.add("Missouri");
+		states.add("Nevada");		
+		
+		// create another ArrayList with null value, 
+		//so that removeAll will throw NullPointerException
+		List<String> statesToBeRemoved =null;
+
+		System.out.println("The states list before the removeAll() method call: \n" + states);
+		
+		// removes all elements specified in the ArrayList statesToBeRemoved 
+		states.removeAll(statesToBeRemoved); 
+		
+		System.out.println("\nThe states list after the removeAll() method call: \n" + states);
+	}
+}

collections/arraylist/arraylist-removeif-method/ArrayListRemoveIfExample.java

@@ -0,0 +1,37 @@
+package com.gaurav.ExProject.ArrayList;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Predicate;
+
+/**
+ * A java program showing an example for the removeIf()
+ * method of the ArrayList class in Java.
+ * 
+ * @author gaurav
+ */
+public class ArrayListRemoveIfExample {
+
+	public static void main(String[] args) {
+
+		// create an empty arraylist object 'states'
+		List<String> states = new ArrayList<String>();
+
+		// add state in the arraylist, Florida multiple times
+		states.add("California");
+		states.add("Texas");
+		states.add("Florida");
+		states.add("Florida");
+		states.add("New Jersey");
+		states.add("Washington");
+		states.add("Florida");
+
+		System.out.println("The states list before the removeIf() call: \n" + states);
+
+		// a predicate for the condition
+		Predicate p = s -> s.equals("Florida");
+		states.removeIf(p); // removes all elements which satisfy the predicate p
+
+		System.out.println("\nThe states list after the removeIf() call: \n" + states);
+	}
+}