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Articles by raja
Page 4 of 38
Can we call the wait() method without acquiring the lock in Java?
No, we cannot call the wait() method without acquiring the lock. In Java, once the lock has been acquired then we need to call wait() method (with timeout or without timeout) on that object. If we are trying to call the wait() method without acquiring a lock, it can throw java.lang.IllegalMonitorStateException. Example public class ThreadStateTest extends Thread { public void run() { try { wait(1000); } catch(InterruptedException ie) { ie.printStackTrace(); ...
Read MoreImportance of yield() method in Java?
A yield() method is a static method of Thread class and it can stop the currently executing thread and will give a chance to other waiting threads of the same priority. If in case there are no waiting threads or if all the waiting threads have low priority then the same thread will continue its execution. The advantage of yield() method is to get a chance to execute other waiting threads so if our current thread takes more time to execute and allocate processor to other threads. Syntax public static void yield() Example class MyThread extends Thread { public void run() { ...
Read MoreHow to instantiate a static inner class with reflection in Java?
A static inner class can be instantiated without the need for an instance of the outer class. In general, an Inner class is a part of nested class, called Non-static nested classes in Java. The types of inner classes are member inner class, anonymous inner class, and local inner class. We can instantiate a static inner class with reflection using InnerClass.class.newInstance(). If we need an instance of the outer class to instantiate a non-static inner class, we can specify it before a new operator. Example import java.lang.reflect.*; public class InnerclassWithReflectionTest { public static void main(String args[]) { ...
Read MoreHow can we implement a custom iterable in Java?
An Iterable interface is defined in java.lang package and introduced with Java 5 version. An object that implements this interface allows it to be the target of the "for-each" statement. This for-each loop is used for iterating over arrays and collections. An Iterable interface can also be implemented to create custom behavior. Syntax public interface Iterable Example import static java.lang.String.format; import java.util.*; // Person class class Person { private String firstName, lastName; private int age; public Person(){ } public Person(String firstName, String lastName, int age) { this.firstName = firstName; ...
Read MoreHow many ways to make an object eligible for GC in Java?
The process of destroying unreferenced objects is called a Garbage Collection(GC). Once an object is unreferenced it is considered as an unused object, hence JVM automatically destroys that object. There are various ways to make an object eligible for GC. By nullifying a reference to an object We can set all the available object references to "null" once the purpose of creating an object is served. Example public class GCTest1 { public static void main(String [] args){ String str = "Welcome to TutorialsPoint"; // String object referenced by variable str and it is not eligible for GC yet. ...
Read MoreHow can we implement a timer thread in Java?
The Timer class schedules a task to run at a given time once or repeatedly. It can also run in the background as a daemon thread. To associate Timer with a daemon thread, there is a constructor with a boolean value. The Timer schedules a task with fixed delay as well as a fixed rate. In a fixed delay, if any execution is delayed by System GC, the other execution will also be delayed and every execution is delayed corresponding to previous execution. In a fixed rate, if any execution is delayed by System GC then 2-3 execution happens consecutively to ...
Read MoreWhat is the importance of a StringWriter in Java?
The StringWriter class is s subclass of Writer class and it writes the String to an output stream. To write a string, this character stream collects the string into a string buffer and then constructed a string. The buffer of StringWriter automatically grows according to data. The important methods of StringWriter class are write(), append(), getBuffer(), flush() and close(). Syntax public class StringWriter extends Writer Example import java.io.*; public class StringWriterTest { public static void main(String args[]) { String str = "Welcome to Tutorials Point"; try { ...
Read MoreWhat is the importance of Runtime class in Java?
The java.lang.Runtime class is a subclass of Object class, can provide access to various information about the environment in which a program is running. The Java run-time environment creates a single instance of this class that is associated with a program. The Runtime class does not have any public constructors, so a program cannot create its own instances of the class. A program must call the getRuntime() method to get a reference to the current Runtime object. The important methods of Runtime class are addShutdownHook(), exec(), exit(), freeMemory(), gc(), halt() and load(). Syntax public class Runtime extends Object Example public class RuntimeTest { ...
Read MoreWhat are the steps to read static members in a Java class?
A static variable gets created at the time of class loading even before the execution of a static block and the purpose of the static block is to assign value to the static variables. A static variable stores a value that is shared between all instances of the class it is defined in and a static block is a section of code that gets executed when class is first loaded. If we want any logic that needs to be executed at the time of class loading that logic needs to place inside the static block so that it will be executed ...
Read MoreWhy an interface cannot implement another interface in Java?
An interface cannot implement another interface in Java. An interface in Java is essentially a special kind of class. Like classes, the interface contains methods and variables. Unlike classes, interfaces are always completely abstract. An interface is defined just like a class except for the keyword interface in place of a class, the variables are declared in an interface are static and final and the methods are defined in an interface are public abstract methods. An interface can extend any number of interfaces but one interface cannot implement another interface, because if any interface is implemented then its methods must be defined and ...
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