Primitive to object conversion in Java - Cheat Sheet & Quick Revision

overview

Recall & Review

beginner

What is primitive to object conversion in Java?

It is the process of converting a primitive data type (like int, double) into its corresponding wrapper class object (like Integer, Double). This allows primitives to be used where objects are required.

beginner

What is autoboxing in Java?

Autoboxing is the automatic conversion by the Java compiler of a primitive type into its corresponding wrapper class object when needed.

beginner

How do you manually convert an int primitive to an Integer object?

You can use the Integer constructor or the static method Integer.valueOf(int). For example: Integer obj = Integer.valueOf(5);

intermediate

What is the difference between autoboxing and manual boxing?

Autoboxing is done automatically by the compiler, while manual boxing requires explicitly creating wrapper objects using constructors or valueOf methods.

beginner

Why is primitive to object conversion useful in Java?

It allows primitives to be used in collections like ArrayList, which only accept objects, and enables use of methods defined in wrapper classes.

Which of these is the wrapper class for the primitive type 'int'?

A Character

B Int

C Integer

D Double

What does autoboxing do in Java?

A Automatically converts primitives to objects

B Converts objects to primitives

C Converts strings to numbers

D Converts objects to strings

Which method can be used to manually convert an int to an Integer?

A Integer.parseInt()

B Integer.valueOf()

C int.toInteger()

D Integer.toInt()

Why can't primitives be added directly to an ArrayList?

A ArrayList only accepts objects

B Primitives are too large

C Primitives are slower

D ArrayList only accepts strings

What is manual boxing?

A Converting a string to a primitive

B Automatically converting a primitive to an object

C Converting an object to a primitive

D Explicitly converting a primitive to its wrapper object

Explain what primitive to object conversion means and why it is important in Java.

Describe the difference between autoboxing and manual boxing with examples.