Object Oriented Programming Articles

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Get first entry from NavigableMap in Java

Samual Sam
Samual Sam
Updated on 11-Mar-2026 213 Views

To display first entry from NavigableMap in Java, use the firstEntry() method.Let us first create NavigableMap −NavigableMap n = new TreeMap(); n.put("A", 498); n.put("B", 389); n.put("C", 868); n.put("D", 988); n.put("E", 686); n.put("F", 888); n.put("G", 999); n.put("H", 444); n.put("I", 555); n.put("J", 666);Get the first entry now −n.firstEntry()The following is an example to get first entry from NavigableMap.Exampleimport java.util.*; public class Demo { public static void main(String[] args) { NavigableMap n = new TreeMap(); n.put("A", 498); n.put("B", 389); ...

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Create a Stack and Queue using ArrayDeque in Java

Samual Sam
Samual Sam
Updated on 11-Mar-2026 611 Views

Create a stack using ArrayDeque.Deque s = new ArrayDeque(); // stack s.push("Bat"); s.push("Mat"); s.push("Cat"); s.push("Rat"); s.push("Hat"); s.push("Fat");Create a queue using ArrayDeque −Deque q = new ArrayDeque(); // queue q.add("Bat"); q.add("Mat"); q.add("Cat"); q.add("Rat"); q.add("Hat"); q.add("Fat");The following is an example.Exampleimport java.util.ArrayDeque; import java.util.Deque; public class Demo {    public static void main(String args[]) {       Deque s = new ArrayDeque();       Deque q = new ArrayDeque();       // stack       s.push("Bat");       s.push("Mat");       s.push("Cat");       s.push("Rat");       s.push("Hat");       s.push("Fat");       ...

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Convert an ArrayList to HashSet in Java

Samual Sam
Samual Sam
Updated on 11-Mar-2026 1K+ Views

To convert ArrayList to HashSet, firstly create an ArrayList −List l = new ArrayList();Add elements to the ArrayList −l.add("Accent"); l.add("Speech"); l.add("Diction"); l.add("Tone"); l.add("Pronunciation");Now convert the ArrayList to HashSet −Set s = new HashSet(l);The following is an example to convert an ArrayList to HashSet in Java.Exampleimport java.util.ArrayList; import java.util.List; import java.util.Set; import java.util.HashSet; public class Main { public static void main(String[] args) { List l = new ArrayList(); l.add("Accent"); l.add("Speech"); l.add("Diction"); ...

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Get the first element from a Sorted Set in Java

Samual Sam
Samual Sam
Updated on 11-Mar-2026 647 Views

To create a Sorted Set, firstly create a Set.Set s = new HashSet();Add elements to the above set.int a[] = {77, 23, 4, 66, 99, 112, 45, 56, 39, 89}; Set s = new HashSet(); try { for(int i = 0; i < 5; i++) { s.add(a[i]); }After that, use TreeSet class to sort.TreeSet sorted = new TreeSet(s);Get the first element, using the first() method −System.out.println("First element of the sorted set = "+ (Integer)sorted.first());The following is the code to get the first element from a Sorted Set ...

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Get last entry from NavigableMap in Java

karthikeya Boyini
karthikeya Boyini
Updated on 11-Mar-2026 242 Views

To display the last entry from NavigableMap in Java, use the lastEntry() method.Let us first create NavigableMap.NavigableMap n = new TreeMap(); n.put("A", 498); n.put("B", 389); n.put("C", 868); n.put("D", 988); n.put("E", 686); n.put("F", 888); n.put("G", 999); n.put("H", 444); n.put("I", 555); n.put("J", 666);Get the last entry now.n.lastEntry()The following is an example to get the last entry from NavigableMap.Exampleimport java.util.*; public class Demo { public static void main(String[] args) { NavigableMap n = new TreeMap(); n.put("A", 498); n.put("B", 389); ...

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How to use headSet() method of Java NavigableSet Class

karthikeya Boyini
karthikeya Boyini
Updated on 11-Mar-2026 163 Views

The headset() method returns elements up to a limit defined as a parameter.First, create a NavigableSet and add elements −NavigableSet set = new TreeSet(); set.add(10); set.add(25); set.add(40); set.add(55); set.add(70); set.add(85); set.add(100);Now, use the headset() method −set.headSet(55));The following is an example −Exampleimport java.util.NavigableSet; import java.util.TreeSet; public class Demo {    public static void main(String[] args) {       NavigableSet set = new TreeSet();       set.add(10);       set.add(25);       set.add(40);       set.add(55);       set.add(70);       set.add(85);       set.add(100);       System.out.println("Returned Value = " + set.headSet(55)); ...

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Create a new ArrayList from another collection in Java

karthikeya Boyini
karthikeya Boyini
Updated on 11-Mar-2026 477 Views

An ArrayList can be created from another collection using the java.util.Arrays.asList() method. A program that demonstrates this is given as follows −Exampleimport java.util.ArrayList; import java.util.Arrays; import java.util.List; public class Demo {    public static void main(String args[]) throws Exception {       String str[] = { "John", "Macy", "Peter", "Susan", "Lucy" };       List aList = new ArrayList(Arrays.asList(str));       System.out.println("The ArrayList elements are: " + aList);    } }OutputThe ArrayList elements are: [John, Macy, Peter, Susan, Lucy]Now let us understand the above program.The string array str[] is defined. Then an ArrayList is created using the ...

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Print a Vector in a comma-delimited list, in index order and surrounded by square brackets ([]) in Java

Arushi
Arushi
Updated on 11-Mar-2026 575 Views

A Vector can be printed in a comma-delimited list, in index order and surrounded by square brackets ([]) by simply using System.out.println() along with the Vector object.A program that demonstrates this is given as follows −Exampleimport java.util.Vector; public class Demo {    public static void main(String args[]) {       Vector vec = new Vector(5);       vec.add(4);       vec.add(1);       vec.add(3);       vec.add(9);       vec.add(6);       System.out.println(vec);    } }The output of the above program is as follows −[4, 1, 3, 9, 6]Now let us understand the ...

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Replace all the elements of a Vector with Collections.fill() in Java

Rishi Raj
Rishi Raj
Updated on 11-Mar-2026 672 Views

All the elements of a vector can be replaced by a specific element using java.util.Collections.fill() method. This method requires two parameters i.e. the Vector and the element that replaces all the elements in the Vector. No value is returned by the Collections.fill() method.A program that demonstrates this is given as follows:Exampleimport java.util.Collections; import java.util.Vector; public class Demo { public static void main(String args[]) { Vector vec = new Vector(5); vec.add(7); vec.add(4); vec.add(1); ...

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Enumerate through the Vector elements in Java

Rishi Raj
Rishi Raj
Updated on 11-Mar-2026 776 Views

The Vector elements can be traversed using the Enumeration interface. The method hasMoreElements( ) returns true if there are more elements to be enumerated and false if there are no more elements to be enumerated. The method nextElement( ) returns the next object in the enumeration.A program that demonstrates this is given as follows −Exampleimport java.util.Enumeration; import java.util.Vector; public class Demo {    public static void main(String args[]) {       Vector vec = new Vector();       vec.add(7);       vec.add(3);       vec.add(5);       vec.add(9);       vec.add(2);       ...

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