What should not be in a constructor?

Don’t use init()/cleanup() members . If you have to call init() every time you create an instance, everything in init() should be in the constructor. The constructor is meant to put the instance into a consistent state which allows any public member to be called with a well-defined behavior.

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What is no constructor in Java?

Java doesn’t require a constructor when we create a class. … The compiler automatically provides a public no-argument constructor for any class without constructors. This is called the default constructor . If we do explicitly declare a constructor of any form, then this automatic insertion by the compiler won’t occur.

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Why do we use constructors in programming?

The sole purpose of the constructor is to initialize the data fields of objects in the class . Java constructor can perform any action but specially designed to perform initializing actions, such as initializing the instance variables. A constructor within a class allows constructing the object of the class at runtime.

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