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Java Articles
Page 70 of 450
Can we write any statements between try, catch and finally blocks in Java?
No, we cannot write any statements in between try, catch and finally blocks and these blocks form one unit. The functionality of try keyword is to identify an exception object and catch that exception object and transfer the control along with the identified exception object to the catch block by suspending the execution of the try block. The functionality of the catch block is to receive the exception class object that has been sent by the try and catch that exception class object and assigns that exception class object to the reference of the corresponding exception class defined in the catch block. The finally blocks are ...
Read MoreWhat are the differences between a static block and a constructor in Java?
Static blockThe static blocks are executed at the time of class loading.The static blocks are executed before running the main () method.The static blocks don't have any name in its prototype.If we want any logic that needs to be executed at the time of class loading that logic needs to placed inside the static block so that it will be executed at the time of class loading.Syntaxstatic { //some statements }Examplepublic class StaticBlockTest { static { System.out.println("Static Block!"); } public static void main(String args[]) { System.out.println("Welcome to Tutorials Point!"); } }OutputStatic Block! Welcome ...
Read MoreHow many types of anonymous inner classes are defined in Java?
An anonymous inner class is an inner class which is declared without any class name at all. In other words, a nameless inner class is called an anonymous inner class. Since it does not have a name, it cannot have a constructor because we know that a constructor name is the same as the class name.We can define an anonymous inner class and create its object using the new operator at the same time in one step.Syntaxnew(argument-list){ // Anonymous class body }Types of Anonymous Inner Class in JavaAnonymous inner class that extends a classAnonymous inner class that implements an interfaceAnonymous inner ...
Read MoreWhen can we use intern() method of String class in Java?
The intern() method of String class can be used to deal with the string duplication problems in Java. Using intern() we can save a lot of memory consumed by duplicate string instances. A string is duplicate if it contains the same content as another string but it can be occupied different memory locations.We know that JVM maintains a separate heap memory for string literals for the performance. Once we declare a string literal it will go to this pool and if another variable is assigned with the same literal value, it will be picked from the pool instead of creating a new ...
Read MoreWhat is an OutOfMemoryError and steps to find the root cause of OOM in Java?
The OutOfMemoryError is thrown by JVM, when JVM does not have enough available memory, to allocate. OutOfMemoryError falls into the Error category in Exception class hierarchy.To generate OutOfMemoryErrorWe will allocate a large chunk of memory, which will exhaust heap memory storage.We will keep on allocating the memory and point will reach, when JVM will not have enough memory to allocate, then OutOfMemoryError will be thrown.Once we will catch the OutOfMemory error, we can log the error.Examplepublic class OutOfMemoryErrorDemo { public static void main(String[] args) throws Exception { int dummyArraySize = 15; System.out.println("Max JVM memory: " + Runtime.getRuntime().maxMemory()); ...
Read MoreCan we define a static constructor in Java?
No, we cannot define a static constructor in Java, If we are trying to define a constructor with the static keyword a compile-time error will occur.In general, static means class level. A constructor will be used to assign initial values for the instance variables. Both static and constructor are different and opposite to each other. We need to assign initial values for an instance variable we can use a constructor. We need to assign static variables we can use Static Blocks.Examplepublic class StaticConstructorTest { int x = 10; // Declaratiopn of Static Constructor static StaticConstructorTest() { ...
Read MoreCan we declare a top level class as protected or private in Java?
No, we cannot declare a top-level class as private or protected. It can be either public or default (no modifier). If it does not have a modifier, it is supposed to have a default access.Syntax// A top level class public class TopLevelClassTest { // Class body }If a top-level class is declared as private the compiler will complain that the modifier private is not allowed here. This means that a top-level class cannot be a private, the same can be applied to protected access specifier also.Protected means that the member can be accessed by any class in the same ...
Read MoreIs it possible to assign a reference to "this" in java?
The "this" keyword in Java is used as a reference to the current object, within an instance method or a constructor. Using it, you can refer the members of a class such as constructors, variables, and methods.Assigning reference to "this"According to the definition "this" is a keyword which acts as a reference to the current object (the object from whose constructor/method you are using it), its value id is fixed. Therefore, you cannot assign a new reference value to it. Moreover, it is just a keyword, not a variable.Still, if you try to it assign a reference value to "this" it ...
Read MoreWhat happens if we call "super()" in a constructor without extending any class, in java?
A super keyword is a reference of the superclass object in Java. Using this, you can invoke the instance methods constructors and, variables, of a superclass.Calling the constructor of a superclassYou can call the constructor of a superclass from the subclass’s constructor.ExampleConsider the following example, it has two classes SuperClass class and SubClass where the SubClass extends the SuperClass. The superclass has a parameterized constructor, we are invoking it from the subclass using the "super" keyword.class SuperClass{ SuperClass(int data){ System.out.println("Superclass's constructor: "+data); } } public class SubClass extends SuperClass{ SubClass(int data) { super(data); ...
Read MoreCan we call Superclass's static method from subclass in Java?
A static method is the one which you can call without instantiating the class. If you want to call a static method of the superclass, you can call it directly using the class name.Examplepublic class Sample{ public static void display(){ System.out.println("This is the static method........"); } public static void main(String args[]){ Sample.display(); } }OutputThis is the static method........It also works, if you call a static method using an instance. But, it is not recommended.public class Sample{ public static void display(){ System.out.println("This is the static method........"); ...
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