Parsing numeric arguments in Java - Cheat Sheet & Quick Revision

overview

Recall & Review

beginner

What is the purpose of parsing numeric arguments in Java?

Parsing numeric arguments means converting strings (like command line inputs) into numbers (like int or double) so the program can use them in calculations.

beginner

Which Java method converts a String to an int?

The method Integer.parseInt(String s) converts a string to an int number.

intermediate

How do you safely handle invalid numeric input when parsing in Java?

Use a try-catch block to catch NumberFormatException. This prevents the program from crashing if the input is not a valid number.

beginner

What is the difference between Integer.parseInt() and Double.parseDouble()?

Integer.parseInt() converts a string to an integer (whole number), while Double.parseDouble() converts a string to a double (decimal number).

intermediate

Why is it important to validate numeric arguments after parsing?

Because even if parsing succeeds, the number might be out of expected range or invalid for the program logic. Validation ensures the program behaves correctly.

Which Java method converts a string "123" to the integer 123?

A Integer.toString(123)

B Double.parseDouble("123")

C String.valueOf(123)

D Integer.parseInt("123")

What exception should you catch when parsing a number from a string in Java?

A NumberFormatException

B IOException

C NullPointerException

D ArithmeticException

Which method would you use to parse a decimal number from a string?

A Double.parseDouble()

B String.parseDouble()

C Integer.parseInt()

D Float.toString()

What happens if you try to parse "abc" as an integer using Integer.parseInt("abc")?

A Returns 0

B Throws NumberFormatException

C Returns null

D Compiles error

Why should you validate numeric arguments after parsing?

A To improve performance

B To convert it back to string

C To check if the number fits program rules

D To avoid syntax errors

Explain how to convert a command line argument to an integer in Java and handle possible errors.

Describe the difference between parsing integers and doubles from strings in Java.