Number Parsing in Karel

Our example demonstrates how to parse numbers from strings in Java, which is a common task in many programs.

import java.util.Scanner;

public class NumberParsing {
    public static void main(String[] args) {
        // With parseDouble, we can parse floating-point numbers
        double f = Double.parseDouble("1.234");
        System.out.println(f);

        // For parseInt, we can specify the radix (base) of the number system
        int i = Integer.parseInt("123", 10);
        System.out.println(i);

        // parseInt will recognize hex-formatted numbers when using radix 16
        int d = Integer.parseInt("1c8", 16);
        System.out.println(d);

        // A parseUnsignedInt is also available for parsing unsigned integers
        int u = Integer.parseUnsignedInt("789");
        System.out.println(u);

        // Integer.parseInt is a convenience method for basic base-10 int parsing
        int k = Integer.parseInt("135");
        System.out.println(k);

        // Parse methods throw NumberFormatException on bad input
        try {
            int bad = Integer.parseInt("wat");
        } catch (NumberFormatException e) {
            System.out.println(e.getMessage());
        }
    }
}

When you run this program, you’ll see the following output:

$ java NumberParsing
1.234
123
456
789
135
For input string: "wat"

In Java, we use the Double.parseDouble() method to parse floating-point numbers, and Integer.parseInt() for parsing integers. The Integer.parseUnsignedInt() method is used for parsing unsigned integers.

For Integer.parseInt(), you can specify the radix (base) of the number system as the second argument. This allows you to parse numbers in different bases, such as hexadecimal.

Java’s parsing methods throw a NumberFormatException when given invalid input, which we catch and handle in a try-catch block.

Next, we’ll look at another common parsing task: URLs.

Writing Files in Karel

Url Parsing in Karel

Learn X By Example

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Number Parsing in Karel