Java Tutorial

Java Tutorial Java Features C++ vs Java Java History Java Hello World Java Development Kit Java Runtime Environment Java Virtual Machine Difference between JDK, JRE, and JVM Memory Areas in Java Java Operators Java Keywords Primitive Data Types Variables

Java Loops

Java Do While Loop Java While Loop Java For Loop Java Enhanced For Loop

Java Programs

Java Basic Programs Factorial Program in Java Fibonacci Series Program in Java Prime Number Program in Java Palindrome Number Program in Java Armstrong Number Program in Java Anagram Program in Java Pattern Programs in Java Calculator Program in Java Leap Year Program in Java Addition Program in Java Number Pattern Programs in Java Star Pattern Programs in Java Package Program in Java Pyramid Program in Java Sorting Program in Java String Palindrome Program in Java Even Odd Program in Java For Loop Program in Java If Else Program in Java Switch Case Program in Java GCD Program in Java LCM Program in Java Hello Program in Java Matrix Program in Java Menu Driven Program in Java Series Program in Java Client Server Program in Java Swapping Program in Java Pig Latin Program in Java Tower of Hanoi Program in Java Recursion Program in Java Matrix Multiplication Program in Java Perfect Number Program in Java Classes and Objects in Java Example Programs String Programs in Java Array Programs in Java Constructor Program in Java Inheritance Program in Java Abstract class Program in Java Interface Program in Java Encapsulation Program in Java Polymorphism Program in Java Exception Handling Program in Java Multithreading Program in Java Thread Program in Java Collection Programs in Java ArrayList Program in Java Stack Program in Java Applet Program in Java Swing Program in Java JDBC Program in Java How to run Java program in command prompt How to run Java program in Eclipse Program to find and replace characters on string in java Program to find the duplicate characters in a string Program to check whether a given character is present in a string or not Java Program to Print Permutations of String Java program to find frequency of characters in a string Java Program to remove duplicate characters in a string

Java Sorting

Sorting Algorithms in Java Merge Sort in Java Quick Sort in Java Bubble Sort in Java Insertion Sort in Java Selection Sort in Java Heap Sort in Java Radix Sort in Java Topological Sort in Java Bucket Sort in Java Counting Sort in Java

Java OOPs Concepts

OOPs - Object Oriented Programming Objects and Classes in Java Methods in Java Java Naming Conventions Constructors in Java Java this keyword Java static keyword Inheritance in Java Aggregation in Java Java super keyword Constructor Chaining and Constructor Overloading Java Polymorphism Static and Dynamic Binding in Java Java Abstraction Abstract class in Java Interface in Java Difference between Abstract class and Interface Java final keyword Packages in Java Access Modifiers in Java Java Wrapper classes Java Numbers Java Characters Java Integer Java Boolean Java Arrays Java Command Line Arguments Java strictfp Keyword Java Math

Java Strings

Java Strings Java String Methods StringBuilder in Java StringBuffer in Java Java Regular Expressions StringBuffer vs StringBuilder String vs StringBuffer String vs StringBuilder String Manipulation in Java Java String Concatenation How to Reverse a String in Java String Array in Java How to Compare Two Strings in Java How to Concatenate Two Strings in Java Why String in Immutable in Java Java.lang.NumberFormatException for Input String String Pool in Java Java Generate Random String How to take String Input in Java Java String Interview Questions

Java Exceptions

Exception Handling in Java Java try catch Java throw Java throws Difference between throw and throws Java finally Java Custom Exception Java Exception Propagation

Garbage Collection

Automatic Resource Management in Java Java Garbage Collection Java finalize() Java gc() Difference between final, finally and finalize


Multithreading in Java Process and Thread in Java Basic Terms in Multithreading Java Thread creation Thread Scheduler in Java Java Thread class DeadLock in Java

Java IO

Java IO Java Read File Java file Reader Java Buffer Reader Java file Writer Java BufferedWriter Java InputStreamReader Scanner in Java Java StringReader Java StringReader Class Java PrintWriter Java File Java Read File Line By Line Java FileInputStream Java FileOutputStream Java Create File Java Delete File Java Open File Java Read File to String Java copy file Java Read JSON file Jar File in Java Java FileNotFoundException


Java Serialization Java transient


Java Network Programming Java Socket Programming Java URL Java URLConnection HttpURLConnection in Java Java InetAddress Java DatagramSocket and Java DatagramPacket


Java AWT


Swing in Java

Java Collections

Collections in Java Java List Interface ArrayList in Java LinkedList in Java Vector in Java Stack in Java ArrayList vs LinkedList in Java ArrayList vs Vector in Java Java Set Interface HashSet in Java LinkedHashSet in Java TreeSet in Java Java Queue Interface PriorityQueue in Java ArrayDeque in Java Java Map Interface HashMap in Java LinkedHashMap in Java TreeMap in Java Dictionary in Java Hashtable in Java Properties in Java Collections class in Java Java Comparable Java Comparator Comparable vs Comparator in Java

Java Generics

Generics in Java

Java Annotations

Annotations in Java


Java JDBC Tutorial JDBC Architecture Types of JDBC Drivers JDBC vs ODBC Java Database Connectivity with MySQL Statements in java Prepared statement in Java Resultset in java Java ResultSetMetaData DatabaseMetaData in Java Callable Statement in Java Transaction Management in java Design of JDBC

Java Differences

Java vs JavaScript Python vs Java Kotlin vs Java Java vs C++ C# vs Java Java float vs double Java vs Scala Static vs Non-static in Java C vs Java int vs Integer in Java Java protected vs private Java vs Dot Net Stack vs Heap in Java Java Array vs ArrayList Java SE vs EE Difference between = = and equals ( ) in java Difference between C, C++, java

How to

How to run Java program How to set path in Java How to check the Java version in cmd How to install Java in Windows 10 How to run Java program in cmd How to add double quotes in a string in Java How to convert list to String in Java How to call a method in Java How to sort an array in Java How to iterate HashMap in Java How to write Java program How to create an array in Java How to create a package in Java How to generate random numbers in Java How to input String in Java How to create thread in Java How to find length of String in Java How to sort a string in Java How to use scanner in Java How to achieve multiple inheritance in Java How to find the length of an Array in Java How to run Java program in Eclipse How to call a function in Java How to create array of objects in Java How to create custom exception in Java How to import packages in Java How to run applet Program in Java How to take Array Input in Java How to achieve abstraction in Java How to call static method in Java How to compare characters in Java How to compare dates in Java How to create a linked list in Java How to get ASCII value of char in Java How to initialize string array in Java How to Install Java on MAC How to run java program in ubuntu How to find characters with the maximum number of times in a string java How to Set Java_home in Linux How to Split the String in Java with Delimiter How to uninstall the Java in Ubuntu How to Split String by Comma in Java How to remove special characters from String in Java How to remove last character from String in Java

Java 8 Features

Java 8 Features Lambda Expressions in Java Functional Interface in Java Streams in Java Java Base64 Encoding and Decoding Java Stringjoiner Class Parallel Arrays Sort in Java

Java 9 Features

Java 9 Tutorial Java 9 Try With Resources Java 9 Interface Private Method

Java 16

Java 16

Java 17

What is new in Java 17

Java Servlet Tutorial

Java Servlets Tutorial

Java JSP Tutorial

Java JSP Tutorial

Hibernate Tutorial

Hibernate Tutorial

Spring Tutorial

Spring Tutorial

Spring MVC Tutorial

Spring MVC Tutorial

Jenkins Tutorial

Jenkins Tutorial

Java Math Methods

Math.abs() Math.acos() Math.addExact() Math.asin() Math.atan () Math.atan2() Math.cbrt() Math.ceil() Math.copysign() Math.cos() Math.cosh() Math.decrementExact() Math.exp() Math.expm1() Math.floor() Math.floorDiv() Math.floorMod() Math.fma() Math.getExponent() Math.hypot() Math.IEEEremainder() Math.incrementExact() Math.log() Math.log10() Math.log1p() Math.max() Math.min() Math.multiplyExact() Math.multiplyFull() Math.negateExact() Math.nextAfter() Math.nextDown() Math.nextUp() Math.pow() Math.random() Math.rint() Math.round() Math.scalb() Math.signum() Math.sin() Math.sinh() Math.sqrt() Math.subtractExact() Math.tan() Math.tanh() Math.toDegrees() Math.toIntExact() Math.toRadians() Math.ulp()

Java String Methods

toCharArray() copyValueOf() endsWith() equals() equalsIgnoreCase() format() getBytes() getChars() hashCode() indexOf() intern() isEmpty() join() lastIndexOf() length() replace() replaceAll() replaceFirst() split() startsWith() subSequence() substring() toLowerCase() toUpperCase() trim() valueOf()

Java Conversion

Java Convert String to int Java Convert int to String Java Convert String to long Java Convert long to String Java Convert String to float Java Convert float to String Java Convert String to double Java Convert double to String Java Convert String to Date Java Convert Date to String Java Convert String to Object Java Convert Object to String Java Convert String to char Java Convert char to String Java Convert int to long Java Convert long to int


Functional Interfaces in Java Singleton class in Java Awesome explanation of Strings in Java Object class in Java Static class in Java All the important string methods in Java String Handling Method in Java What are Array strings in Java Advantages and Disadvantages of Strings in Java Big Decimal class in Java Class definition in Java Char and String differences in Java Difference between String, StringBuffer and StringBuilder in java Replace character in string Java String Coding Interview Questions in Java What is String in Java? String isnullorempty in Java String Matches in Java Trim Method in String Java Bean class in Java Libraries in Java Arithmetic Operations on String in Java Convert Char array to string in java Check whether Java is installed or not How to calculate time difference in Java How to stop execution after a certain time in Java Jagged Array in Java Java ArraylistRemove() Time Complexity Java Swing Time Picker Zigzag Array in Java Array and String based questions in Java Array and String with Examples in Java Best Practices to use String Class in Java What is string in Java why it's immutable Java String Java String Inbuilt functions Java String Matches vs Contains Sum of digits in string in java Check the presence of Substring in a String in java Java import packages Interfaces and Classes in Strings in Java Maximum length of string in java Hidden classes in Java Class memory in Java public static void main string args meaning in java Reverse a String in Java String Concatenation in Java Difference between String and Char Array in Java Buffer reader to read string in Java Split String into String Array in Java Reverse a String using Collections in Java Upcasting and Downcasting in Java String Declaration in Java Method Overloading In Java Java Solid Principles Java Architecture Binary Search Java Star Program in Java Java Type Casting Java Pass-by-Reference Java Framework List Java Destructors Java Control Statements Java Byte Code Java Beans Java Identifiers Character Array in Java Java Applications Java Substring Java Session Non-primitive data types in Java Matrix Multiplication in Java JIT in Java Java Tokens Java Externalization Default Virtual Behaviour in C++ vs Java Why we use static in Java Session Tracking in Java Knapsack problem in Java Java Logo Java exception list Java Iterator Java instance variable Frugal number in Java Fork Join in Java Date time API in java Compile time vs Runtime in java Compare time in java AES 256 Encryption in Java Advanced Java skills What is advance Java? User Defined Exception in Java Upcasting in Java Tree Implementation in Java Special Operators in Java Reentrant Lock in Java Perfect Number in Java Java logger Java LinkedList vs ArrayList File Operation in Java Differences between Byte Code and Machine Code Difference between String Tokenizer and split Method in Java Difference between JIT and JVM in Java Constructor Overloading in Java Conditional operator in Java Concurrent Linked Deque in Java with Examples Command Class in Java Java Break Keyword Best Java IDE Association in Java Access specifiers in Java

Reentrant Lock in Java

The Lock interface is implemented by the ReentrantLock class, which also provides methods for synchronising access to shared resources. The code that controls the resource has calls to the lock and unlock functions all over it. This gives the active thread a lock on the resource and prohibits any other threads from attempting to do so.

ReentrantLock, as its name suggests, enables multiple entries by a thread into the lock on a resource. When the thread initially enters the lock, a hold count is initiated at one. Each time a thread enters lock before being released, the  count goes up by one. When the hold count reaches zero, the resource is released. The count drops by one for each unlocking request.

When a resource is unlocked, reentrant locks also include an option that guarantees that the lock will always allow access to the thread which is waiting. This option is set up by passing true to the function Object() in native code.

Synchronization vs Reentrant Lock:

The synchronised keyword is typically used in Java to create thread synchronisation. The synchronised keyword is rather rigorous in its application, despite the fact that it offers some basic synchronisation. For instance, a thread can only accept a lock once. Because synchronised blocks lack a waiting queue mechanism, any thread can take the lock once a thread exits. This could cause some other thread to run out of resources for a very long time.

Java has reentrant locks to offer synchronisation with more flexibility.

  • Fairness is another important distinction between ReentrantLock and the synchronised keyword. The term "synchronised" opposes fairness. No preference may be provided, and once the lock is released it can be acquired by any thread. ReentrantLock can be made fair by supplying the fairness property when creating an instance of the lock. If there is a dispute, the fairness property grants a lock to the thread that has been waiting for the longest.
  • TryLock() method is the second distinction between synchronised and reentrant locks. A handy tryLock() function is provided by ReentrantLock, which only gets lock if it is available and not being held by another thread. This lessens the blocking caused by threads waiting for Java apps to lock in.
  • Another distinction between ReentrantLock and Java's synchronised keyword is the latter's ability to stop threads while they are waiting for locks. There was no way to prevent a thread from becoming stuck waiting for a lock in the case of a synchronised keyword for an endless amount of time. When a thread is waiting for a lock, ReentrantLock's lockInterruptibly() function allows for interruption. If the lock is unavailable for a predetermined amount of time, tryLock() with timeout can be used to time out.

Thus, it is clear that there are several major distinctions between Java's ReentrantLock and the synchronised keyword. In summary, the Lock interface offers a great deal of flexibility and power and gives users considerable control over the lock acquisition process. This feature may be used to create extremely scalable Java applications.

The following are some significant Java Lock API interfaces and classes:

  • Lock: This is the Lock API's fundamental interface. It offers all the benefits of a synchronised keyword along with extra options to define unique locking conditions and a timeout functionality for threads to wait for a lock. A few crucial methods are lock(), which acquires the lock, unlock(), tryLock(), which waits for the lock for a predetermined amount of time, and newCondition(), which creates the condition, among others.
  • Condition: Condition objects have the added capability of creating several sets of wait, comparable to the Object wait-notify model. Lock objects always produce a Condition object. Await(), which is comparable to wait() and signal(), signalAll(), which is comparable to notify() and notifyAll() techniques, are a few of the crucial methods.
  • ReadWriteLock: One lock is for read-only activities, and the other is for writing. This lock is known as the ReadWriteLock. As long as there are no writer threads, several reader threads may hold the read lock concurrently. There is an exclusive write lock.
  • ReentrantLock: The Lock interface's most popular implementation class. The Lock interface is implemented by this class in a manner comparable to the synchronised keyword. ReentrantLock has several utility methods to access the threads holding the lock, threads waiting to acquire the lock, etc. in addition to implementing the Lock interface. Because synchronised blocks must have the lock on the same monitor object in order to function, a thread can enter a synchronised block if it has the monitor object lock and another synchronised block needs it. ReentrantLock, I believe, is the name of the class for this reason.


Import java.util.*;
class ReentrantLock {

ReentrantLock lock = new ReentrantLock();
 int c = 0;

     int Count() {
        try {
            System.out.println(Thread.currentThread().getName() + " Count: " + count);
            return c++;
        } finally {
     int CountTwo() {
            return c++;

    public static void main(String args[]) {
        ThreadTest cn = new ThreadTest();
        Thread t3 = new Thread() {
            public void run() {
                while (cn.Count() < 6) {
                    try {
                    } catch (InterruptedException ex) {
                        ex.printStackTrace();                    }
        Thread t4 = new Thread() {
            public void run() {
                while (counter.getCount() < 4) {
                    try {
                    } catch (Exception e) {


Thread-0 Count: 0
Thread-1 Count: 1
Thread-1 Count: 2
Thread-0  Count: 3