Why object class in java

Improve this answer. Bozho Bozho k gold badges silver badges bronze badges. And it's fun to think about this further. The Class class inherits from Object itself. You can reflect on reflection. It makes me want to hurt people. Cue the flames In a way, yes. In fact, it's a "class literal" - that's the way you refer to the Class object by name. Show 3 more comments. It's basically syntactic sugar. It is something the compiler evaluates to something that loads the class object with the given name.

Roughly equivalent to Class. ColinD ColinD k 28 28 gold badges silver badges bronze badges. Koray Tugay Koray Tugay Below quote taken from javadoc of class should answer your question Class has no public constructor. Pakka Techie Pakka Techie 5 5 silver badges 6 6 bronze badges. Here is the top level view,. Hope this makes sense. Brendon Cheung Brendon Cheung 9 9 silver badges 23 23 bronze badges. Am I right here? Brendon Cheung when you said 'a Class object that represents that class' , it's a class, not the instance of that class, so I think we should modify the expression.

Because only 'instances' go into heap memory, not their class. Ishanka Abeysinghe Ishanka Abeysinghe 9 2 2 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. For Example, Pen is an object.

Its name is Reynolds; color is white, known as its state. It is used to write, so writing is its behavior. An object is an instance of a class. A class is a template or blueprint from which objects are created. So, an object is the instance result of a class. A class is a group of objects which have common properties. It is a template or blueprint from which objects are created. It is a logical entity. It can't be physical. A variable which is created inside the class but outside the method is known as an instance variable.

Instance variable doesn't get memory at compile time. It gets memory at runtime when an object or instance is created. That is why it is known as an instance variable.

The new keyword is used to allocate memory at runtime. All objects get memory in Heap memory area. In this example, we have created a Student class which has two data members id and name.

We are creating the object of the Student class by new keyword and printing the object's value. In real time development, we create classes and use it from another class. It is a better approach than previous one. Let's see a simple example, where we are having main method in another class. We can have multiple classes in different Java files or single Java file. If you define multiple classes in a single Java source file, it is a good idea to save the file name with the class name which has main method.

Initializing an object means storing data into the object. Let's see a simple example where we are going to initialize the object through a reference variable. In this example, we are creating the two objects of Student class and initializing the value to these objects by invoking the insertRecord method. Here, we are displaying the state data of the objects by invoking the displayInformation method.

As you can see in the above figure, object gets the memory in heap memory area. The reference variable refers to the object allocated in the heap memory area. Here, s1 and s2 both are reference variables that refer to the objects allocated in memory.

Anonymous simply means nameless. An object which has no reference is known as an anonymous object. It can be used at the time of object creation only. JavaTpoint offers too many high quality services. Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Parameters: obj - the reference object with which to compare. Returns: true if this object is the same as the obj argument; false otherwise. The precise meaning of "copy" may depend on the class of the object. The general intent is that, for any object x , the expression: x. While it is typically the case that: x. By convention, the returned object should be obtained by calling super.

If a class and all of its superclasses except Object obey this convention, it will be the case that x. By convention, the object returned by this method should be independent of this object which is being cloned. To achieve this independence, it may be necessary to modify one or more fields of the object returned by super.

Typically, this means copying any mutable objects that comprise the internal "deep structure" of the object being cloned and replacing the references to these objects with references to the copies. If a class contains only primitive fields or references to immutable objects, then it is usually the case that no fields in the object returned by super.

The method clone for class Object performs a specific cloning operation. First, if the class of this object does not implement the interface Cloneable , then a CloneNotSupportedException is thrown. Note that all arrays are considered to implement the interface Cloneable and that the return type of the clone method of an array type T[] is T[] where T is any reference or primitive type.

Otherwise, this method creates a new instance of the class of this object and initializes all its fields with exactly the contents of the corresponding fields of this object, as if by assignment; the contents of the fields are not themselves cloned. Thus, this method performs a "shallow copy" of this object, not a "deep copy" operation. The class Object does not itself implement the interface Cloneable , so calling the clone method on an object whose class is Object will result in throwing an exception at run time.

Returns: a clone of this instance. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read.

It is recommended that all subclasses override this method. In other words, this method returns a string equal to the value of: getClass. If any threads are waiting on this object, one of them is chosen to be awakened.

The choice is arbitrary and occurs at the discretion of the implementation. A thread waits on an object's monitor by calling one of the wait methods. The awakened thread will not be able to proceed until the current thread relinquishes the lock on this object. The awakened thread will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened thread enjoys no reliable privilege or disadvantage in being the next thread to lock this object.

This method should only be called by a thread that is the owner of this object's monitor. A thread becomes the owner of the object's monitor in one of three ways: By executing a synchronized instance method of that object. By executing the body of a synchronized statement that synchronizes on the object. For objects of type Class, by executing a synchronized static method of that class. Only one thread at a time can own an object's monitor.

Throws: IllegalMonitorStateException - if the current thread is not the owner of this object's monitor. See Also: notifyAll , wait notifyAll public final void notifyAll Wakes up all threads that are waiting on this object's monitor. The awakened threads will not be able to proceed until the current thread relinquishes the lock on this object. The awakened threads will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened threads enjoy no reliable privilege or disadvantage in being the next thread to lock this object.

See the notify method for a description of the ways in which a thread can become the owner of a monitor. See Also: notify , wait wait public final void wait long timeout throws InterruptedException Causes the current thread to wait until either another thread invokes the notify method or the notifyAll method for this object, or a specified amount of time has elapsed.