It will take you to some of the most important topics for Java and JEE interviews, worth reading even if you are not preparing for Java interview. I am sure you have seen many of these questions personally on your interviews and many of you would have answered them correctly as well. This is one of the tricky Java multi-threading questions you will see in senior Java developer Interview.
Since we can not modify the size of an array after creating it, we prefer to use ArrayList in Java which re-size itself automatically once it gets full.
ArrayList in Java implements List interface and allow null. Java ArrayList also maintains insertion order of elements and allows duplicates opposite to any Set implementation which doesn't allow duplicates.
But while java copy on write arraylist methods ListIterator you need to be little careful because ListIterator has no current element; its cursor position always lies between the element that would be returned by a call to previous and the element that would be returned by a call to next.
ArrayList has been modified in Java 5 Tiger to support Generics which makes Java ArrayList even more powerful because of enhanced type-safety. Before Java5 since there was no generics no type checking at compile time which means there is a chance of storing different type of element in an ArrayList which is meant for something and ultimately results in ClassCastException during runtime.
If multiple threads access a Java ArrayList instance concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally.
As per Java doc a structural modification is any operation that adds or deletes one or more elements, or explicitly re-sizes the backing array; merely setting the value of an element is not a structural modification.
This is typically accomplished by synchronizing on some object that naturally encapsulates the list. If no such object exists, the list should be "wrapped" using the Collections.
Another better option is to use CopyOnWriteArrayList which is added from Java 5 and optimized for multiple concurrent read. Please let me know if you need any other Java ArrayList examples and I will add them here.
Java ArrayList Example 1: How to create an ArrayList You can use ArrayList in Java with or without Generics both are permitted by generics version is recommended because of enhanced type-safety. In this example, we will create an ArrayList of String in Java.
This Java ArrayList will only allow String and will throw a compilation error if we try to any other object than String. If you notice you need to specify the type on both right and left the side of the expression, from Java 1.
This can save a lot of space if you are defining an ArrayList of nested types. Since we are using Generics and this is an ArrayList of String, the second line will result in a compilation error because this Java ArrayList will only allow String elements.
You can easily find a number of elements in ArrayList by calling size method on it. Remember this could be different with the length of the array which is backing ArrayList. When you use this method, ArrayList internally uses equals method to find the object, so make sure your element implements equals and hashCode or else Object class' default implementation will be used, which compares object based upon memory location.
Here are two ways of doing it without using Iterator. We will see the use of Iterator in next section.Resizable-array implementation of the List interface.
Implements all optional list operations, and permits all elements, including torosgazete.com addition to implementing the List interface, this class provides methods to manipulate the size of the array that is used internally to store the list.
(This class is roughly equivalent to Vector, except that it is unsynchronized.). Java CopyOnWriteArrayList is a thread-safe variant of ArrayList in which all mutative operations (add, set, and so on) are implemented by making a fresh copy of the underlying array. It’s immutable snapshot style iterator method uses a reference to the state of the array at the point that the iterator was created.
Java is defined by a specification and consists of a programming language, a compiler, core libraries and a runtime (Java virtual machine) The Java runtime allows software developers to write program code in other languages than the Java programming language which still runs on the Java virtual machine.
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The C# language is an object-oriented language that is aimed at enabling programmers to quickly build a wide range of applications for the torosgazete.com platform.
Answer: clone() - Creates and returns a copy of this object. equals() - Indicates whether some other object is "equal to" this one. finalize() - Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.