Can you use this () and super () both in a constructor?

Use of both super() and this() are restricted by the condition that they can be used only as the first statement of a constructor. Both cannot be the first statement at the same time and so cannot be used together in the same constructor.

Can we use this () and super () in a constructor?

If we include “this()” or “super()” inside the constructor, it must be the first statement inside it. “this()” and “super()” cannot be used inside the same constructor, as both cannot be executed at once (both cannot be the first statement). “this” can be passed as an argument in the method and constructor calls.

Can we use this () and super () in a method in Java?

No. this keyword mainly represents the current instance of a class. On other hand super keyword represents the current instance of a parent class. this keyword used to call default constructor of the same class.

Why can't we use super and this in static method?

Where the "super" keyword in Java is used as a reference to the object of the superclass. This implies that to use "super" the method should be invoked by an object, which static methods are not. Therefore, you cannot use the "super" keyword from a static method.

What would be the behavior if this () and super () used in a method?

2. What would be the behaviour if this() and super() used in a method? Explanation: this() and super() cannot be used in a method. This throws compile time error.

Java Super Keyword Tutorial - Super Keyword for Variables, Constructors and Methods

Can we use this in constructor?

It can be used inside the method or constructor of a class. It(this) works as a reference to the current object, whose method or constructor is being invoked. This keyword can refer to any member of the current object from within an instance method or a constructor.

Can constructor be Synchronised?

Note that constructors cannot be synchronized — using the synchronized keyword with a constructor is a syntax error. Synchronizing constructors doesn't make sense, because only the thread that creates an object should have access to it while it is being constructed.

Can constructor be overloaded?

Constructors can be overloaded in a similar way as function overloading. Overloaded constructors have the same name (name of the class) but the different number of arguments. Depending upon the number and type of arguments passed, the corresponding constructor is called.

Can constructor have a return type?

Constructors do not return any type while method(s) have the return type or void if does not return any value. Constructors are called only once at the time of Object creation while method(s) can be called any number of times.

Can constructor be static 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.

What is this () in constructor?

The this() constructor call can be used to invoke the current class constructor. It is used to reuse the constructor. In other words, it is used for constructor chaining.

Can I call method in constructor?

Yes, as mentioned we can call all the members of a class (methods, variables, and constructors) from instance methods or, constructors.

What is super () used for in Java?

The super keyword refers to superclass (parent) objects. It is used to call superclass methods, and to access the superclass constructor. The most common use of the super keyword is to eliminate the confusion between superclasses and subclasses that have methods with the same name.

Is super () necessary Java?

If we call "super()" without any superclass

Actually, nothing will be displayed. Since the class named Object is the superclass of all classes in Java.

What is difference between this and super in Java?

super keyword is used to access methods of the parent class while this is used to access methods of the current class. this is a reserved keyword in java i.e, we can't use it as an identifier. this is used to refer current-class's instance as well as static members.

How do you call a superclass constructor?

To explicitly call the superclass constructor from the subclass constructor, we use super() . It's a special form of the super keyword. super() can be used only inside the subclass constructor and must be the first statement.

Can we override constructor in Java?

It does not have a return type and its name is same as the class name. But, a constructor cannot be overridden. If you try to write a super class's constructor in the sub class compiler treats it as a method and expects a return type and generates a compile time error.

Why constructor has no return type?

So the reason the constructor doesn't return a value is because it's not called directly by your code, it's called by the memory allocation and object initialization code in the runtime. Its return value (if it actually has one when compiled down to machine code) is opaque to the user - therefore, you can't specify it.

Can we call constructor without creating object?

NO. You can't invoke a constructor without creating an object.

What is this () in Java?

Definition and Usage

The this keyword refers to the current object in a method or constructor. The most common use of the this keyword is to eliminate the confusion between class attributes and parameters with the same name (because a class attribute is shadowed by a method or constructor parameter).

Can we use this keyword in static method?

No, we can't use “this” keyword inside a static method. “this” refers to current instance of the class. But if we define a method as static , class instance will not have access to it, only CLR executes that block of code. Hence we can't use “this” keyword inside static method.

Can we use this keyword in method?

The "this" keyword in Java is used as a reference to the current object, within an instance method or a constructor. Yes, you can call methods using it.

Can constructor be void?

Note that the constructor name must match the class name, and it cannot have a return type (like void ). Also note that the constructor is called when the object is created.

Can a constructor be virtual?

Constructor can not be virtual, because when constructor of a class is executed there is no vtable in the memory, means no virtual pointer defined yet.

Can we use final keyword before constructor?

declaring constructor as final

In other words, constructors cannot be inherited in Java, therefore, you cannot override constructors. So, writing final before constructors make no sense. Therefore, java does not allow final keyword before a constructor.