Default values in Java - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are default values in Java?

Default values are the initial values assigned automatically to variables when they are declared but not explicitly initialized.

beginner

What is the default value of an int variable in Java?

The default value of an int variable is 0.

beginner

What default value does a boolean variable have in Java?

A boolean variable defaults to false if not initialized.

beginner

What is the default value of a reference type variable (like an object) in Java?

Reference type variables default to null if not initialized.

intermediate

Do local variables in Java have default values?

No, local variables do not have default values and must be initialized before use.

What is the default value of a char variable in Java?

A '\u0000' (null character)

B ' ' (space character)

C '0' (zero character)

D No default value

The default value of a char variable is the null character '\u0000'.

Which of these variables will NOT have a default value in Java?

A Local variables

B Static variables

C Instance variables

D Class variables

Local variables must be initialized before use; they do not get default values.

What is the default value of a double variable in Java?

A 0

B 0.0

C null

D NaN

The default value of a double variable is 0.0.

What default value does a String variable have in Java?

A "null" (string literal)

B "" (empty string)

C null

D No default value

String is a reference type, so its default value is null.

Why is it important to initialize local variables in Java?

A Because they have random default values

B Because they are final

C Because they are static

D Because they do not have default values

Local variables do not have default values and must be initialized before use to avoid errors.

Explain what default values are in Java and give examples for at least three data types.

Think about what happens if you declare a variable but don't assign a value.

Why do local variables in Java require explicit initialization before use?

Consider the difference between local and instance variables.