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Difference between wait() and sleep() in java ?

Editor — Sat, 17 Jul 2021 08:21:15 +0000

Wait() Method	Sleep() Method
wait() Method of thread class goes in waiting state and it won’t come back automatically until we call the notify() or notifyAll().	sleep() is a method which is used to pause the process for few seconds or the time we want too.
It is called on Object.	It is called on Threads.
It is an instant member of java.lang.Object class.	It is a static member of java.lang.Thread class.
wait() releases the lock or monitor.	sleep() doesn’t releases the lock or monitor while waiting.
wait() is used for inter-thread communication.	sleep() is used to introduce pause on execution, generally.
It must be called within the synchronized blocks.	It may be called from within or outside the synchronized block.
wait() Example synchronized(LOCK) { LOCK.wait(); // LOCK is not held }	sleep() Example synchronized(LOCK) { Thread.sleep(1000); // LOCK is held }

Editor — Wed, 14 Jul 2021 00:03:41 +0000

ClassNotFoundException and NoClassDefFoundError occur when a particular class is not found at runtime. However, they occur at different scenarios.
ClassNotFoundException is an exception that occurs when you try to load a class at run time using Class.forName() or loadClass() methods and mentioned classes are not found in the classpath.
NoClassDefFoundError is an error that occurs when a particular class is present at compile time, but was missing at run time.

NoClassDefFoundError	ClassNotFoundException
NoClassDefFoundError is an error. It is the type of java.lang.Error.	ClassNotFoundException is an exception. It is the type of java.lang.Exception.
It occurs when java runtime system doesn’t find a class definition, which is present at compile time, but missing at run time.	It occurs when an application tries to load a class at run time which is not updated in the classpath.
It is thrown by the Java Runtime System.	It is thrown by the application itself. It is thrown by the methods like Class.forName(), loadClass() and findSystemClass().
It occurs when required class definition is missing at runtime.	It occurs when classpath is not updated wih required JAR files.

Editor — Wed, 14 Jul 2021 00:03:36 +0000

Java Development Kit is the core component of Java Environment and provides all the tools, executables and binaries required to compile, debug and execute a Java Program.
JDK is a platform specific software and thats why we have separate installers for Windows, Mac and Unix systems.
We can say that JDK is superset of JRE since it contains JRE with Java compiler, debugger and core classes. Current version of JDK is 1.7 also known as Java 7.

JVM is the heart of java programming language. When we run a program, JVM is responsible to converting Byte code to the machine specific code.
JVM is also stage dependent and provides core java functions like memory management, garbage collection, security etc.
JVM is customizable and we can use java options to modify it, for example allocating minimum and maximum memory to JVM. JVM is called virtual because it delivers a interface that does not depend on the underlying operating system and machine hardware.
This independence from hardware and operating system is what makes java program write-once run-anywhere.

JRE is the implementation of JVM, it provides platform to execute java programs. JRE consists of JVM and java binaries and other classes to execute any program successfully.
JRE doesn’t contain any development tools like java compiler, debugger etc.
If you want to execute any java program, you should have JRE installed but we don’t need JDK for running any java program.

JDK	JRE	JVM
Java Development Kit	Java Runtime environment.	Java Virtual Machine.
Kit providing the platform to develop and execute/run the java program.	It is an installation package which provides environment to only run(not develop) the java program (or application)onto your machine.	Whatever Java program you run using JRE or JDK goes into JVM and JVM is responsible for executing the java program line by line hence it is also known as interpreter.
JDK is only used by Java Developers.	JRE is only used by them who only wants to run the Java Programs (i.e). end users of your system.	It is in-built in both JDK and JRE.

Editor — Tue, 13 Jul 2021 17:09:42 +0000

Array	Linked List
Arrays are index-based data structure where each element associated with an index.	Linked list relies on references where each node consists of the data and the references to the previous and next element (in case of a doubly linked list) or the next element (in case of a singly linked list).
Array provides fast and random access.	Elements can’t be accessed randomly but can be accessed only sequentially and accessing element takes 0(n) time.
Elements are stored in consecutive manner in memory.	Elements can be stored at any available place as address of node is stored in previous node.
Insertion & deletion takes more time in array as elements are stored in consecutive memory locations.	Insertion & deletion are fast & easy in linked list as only value of pointer is needed to change.
In array, memory is allocated at compile time i.e. Static Memory Allocation.	Memory is allocated at run time i.e. Dynamic Memory Allocation.
Array can be single dimensional, two dimensional or multidimensional.	Linked list can be singly, doubly or circular linked list.
Each element is independent, no connection with previous element or with its location.	Location or address of elements is stored in the link part of previous element/node.