Number Classes In Java With Example And Best Explanation

The Number class In Java is the superclass of BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, and Short.

The subclasses of Number must have methods for converting the represented number to byte, double, float, int, long, and short.

What is Number Classes in Java

The Java Number Class is an abstract class that is placed in the java.lang package.

It has two concrete methods and four abstract methods.

The classes BigDecimal, BigInteger, Byte, Double, Float, Integer, Long, and Short are all subclasses of the abstract class Number.

This class only has one constructor number ().

What is the Use of Number Class

The main use of this Number class In Java is to provide methods for converting the number in question to primitive types like byte, short, int, long, double, and float.

Without further ado, I will explain it in a simple way.

Usually, when we work with Number Class, we use primitive data types like byte, int, long, double, etc.

Number Class In Java Example

int number = 6000;
float gpa = 14.65f;
double fuel = 155;

But there are times in development when we need to use objects instead of primitive data types.

Wrapper classes are part of Java so this can be done.

The number is an abstract class, and all of the wrapper classes (Integer, Long, Byte, Double, Float, and Short) are subclasses of it.

The object of the wrapper class holds or wraps its respective primitive data type.

Boxing is the process of converting primitive data types into objects, which is taken care of by the compiler.

So, when using a wrapper class, you just need to pass the value of the primitive data type to the constructor of the wrapper class.

And the Wrapper object will be turned back into a primitive data type.

This process is called “unboxing.” The Number class is a part of the java.lang package.

Here is an example of boxing and unboxing

Number Class In Java Example Program

// program by Glenn Magada Azuelo
public class Test {

   public static void main(String args[]) {
      Integer x = 43; // boxes int to an Integer object
      x =  x + 10;   // unboxes the Integer to a int
      System.out.println(x); 
   }
}

Output:

53

In order for you to test the Java code provided in this lesson, you must test the code in your code editor.

You can test the above example here! ➡Java Online Compiler 

When an integer value is given to x, which is an integer object, the compiler boxes the integer.

Later, x is taken out of its box so that the numbers can be added as a whole.

Number Methods

Here is a list of the instance methods that all of the Number class’s subclasses use.

Conclusion

In this article, we talked about Number Classes In Java, how they work and what they’re used for, and how this chapter can make it easier for you to learn Java.

This could be one of the most helpful ways to learn how to be a better Java developer.

What’s Next

In the next section, we’ll talk about the Character Class In Java. You will learn how to use object Characters and the simple data type char in Java.

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Modern Java file I/O patterns

• Files.readString / writeString. Java 11+ one-liners for whole-file text.
• Files.readAllLines / lines. readAllLines loads everything into memory. lines returns a Stream for large-file streaming.
• Files.newBufferedReader / Writer. Modern replacement for FileReader/FileWriter with encoding control.
• Path vs File. Prefer Path (java.nio.file) , richer API, better error handling.
• StandardCharsets.UTF_8. Explicit encoding avoids platform-dependent bugs.

Working code example

import java.nio.file.*;
import java.io.*;
import java.util.stream.*;

public class FileIOPatterns {
    // Read whole file (small files)
    public String readAll(String path) throws IOException {
        return Files.readString(Paths.get(path));
    }

    // Stream lines (large files)
    public long countErrorLines(String path) throws IOException {
        try (Stream<String> lines = Files.lines(Paths.get(path))) {
            return lines.filter(l -> l.contains("ERROR")).count();
        }
    }

    // Write text
    public void writeReport(String path, String data) throws IOException {
        Files.writeString(Paths.get(path), data,
            StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
    }
}

Common pitfalls

• Forgetting to close streams. Use try-with-resources , never rely on garbage collection.
• Loading huge files with readAllLines. Use Files.lines with a Stream for anything large.
• Assuming platform default encoding. Windows may default to windows-1252, Linux to UTF-8 , explicit encoding avoids surprises.

Best practices

• Path.of / Paths.get. Preferred over new File() , the entire nio.file API works with Path.
• Use StandardCharsets.UTF_8. Explicit charset in every read/write.
• Use Files.walk for directory traversal. Streaming API , cleaner than recursive listFiles().

Glenn Azuelo

Programmer & Technical Writer at PIES IT Solution

Glenn Azuelo is a programmer and writer at PIES IT Solution, author of 40+ PHP tutorials, Java capstone projects, and Python game guides at itsourcecode.com. Specializes in PHP built-in functions (string manipulation, arrays, filesystem, magic methods), Java Windows Forms projects for BSIT capstone (chat application, POS, faculty management, memory game), and Python game programming with Pygame (chess, blackjack, dice).

Expertise: PHP, PHP Tutorials, PHP Built-in Functions, PHP String Functions, PHP Array Functions, PHP Magic Methods, Java, Java Swing, Windows Forms, Python, Pygame, Capstone Projects  ·  View all posts by Glenn Azuelo →