🚀 Programming Example

Java Program to Demonstrate the float Data Type

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Java Java 8 or later

Beginner

Demonstration

Learn how to declare, initialise and print float variables in Java. This program explains why the f suffix is required and shows that float keeps only about 7 significant digits. It also prints the range of the type using Float.MAX_VALUE and Float.MIN_VALUE.

Before You Begin

What you will learn

Declare and initialise variables of the float data type
Understand why a float literal needs the f or F suffix
Know that float uses 4 bytes and keeps about 7 significant digits
Print the range of float using Float.MAX_VALUE and Float.MIN_VALUE
Join text and values in output using the + operator
Choose between float and double

Prerequisites

JDK (Java Development Kit) installed on your computer
Basic structure of a Java program: a class and the main() method
How to print output with System.out.println()
What a variable is and how to declare one
Single-line comments using //

📌 Information & Algorithm

Algorithm

Start
Create a public class named FloatDataType.
Define the main() method.
Declare float variable a and assign it 234.5f.
Declare float variable b and assign it 234.565f.
Display the values of a and b.
Declare float variable pi with a long decimal value and display it, showing that only about 7 digits are kept.
Display Float.MAX_VALUE and Float.MIN_VALUE.
Stop

How to Run

Environment: JDK (Windows, Linux, macOS)

Execution command:

javac FloatDataType.java
java FloatDataType

💻 Program Code

public class FloatDataType {

    public static void main(String[] args) {

        // Declare and initialise float variables
        // The 'f' suffix tells Java the literal is a float, not a double
        float a = 234.5f;
        float b = 234.565f;

        System.out.println("a = " + a);
        System.out.println("b = " + b);

        // float keeps only about 7 significant digits
        float pi = 3.14159265358979f;
        System.out.println("pi = " + pi);

        // Range of the float data type
        System.out.println("Max float value = " + Float.MAX_VALUE);
        System.out.println("Min float value = " + Float.MIN_VALUE);
    }
}

Sample Input

No input required

🖥 Program Output

                                a = 234.5
b = 234.565
pi = 3.1415927
Max float value = 3.4028235E38
Min float value = 1.4E-45

📘 Explanation

Overview

float is a primitive data type that stores decimal (floating-point) numbers. It uses 4 bytes (32 bits) of memory and keeps about 7 significant digits. It's a good choice when you need decimals and want to save memory, and you don't need high precision.

Java treats every decimal literal like 234.5 as a double by default. Add f or F at the end to make it a float.

Step-by-Step Explanation

Declare and Initialise float Variables

The f suffix is required.

float a = 234.5f;
float b = 234.565f;

float is the data type, a and b are the variable names, and 234.5f and 234.565f are float literals. Without the f, Java gives a compile error because it can't automatically convert a double into a smaller float.

Print the Values

Text and values joined with +.

System.out.println("a = " + a);
System.out.println("b = " + b);

The + operator joins the text and the variable's value. The f suffix isn't printed, so the output is a = 234.5 and b = 234.565.

Limited Precision

Only about 7 significant digits are kept.

float pi = 3.14159265358979f;
System.out.println("pi = " + pi);

The value has 15 digits, but float can't store that many. Java rounds it, so the output is 3.1415927. If you need more precision, use double.

Range of float

Largest and smallest positive values.

System.out.println("Max float value = " + Float.MAX_VALUE);
System.out.println("Min float value = " + Float.MIN_VALUE);

Float.MAX_VALUE is the largest float, 3.4028235E38. Float.MIN_VALUE is the smallest positive float, 1.4E-45, not the most negative one. E38 means "× 10³⁸".

float at a Glance

Property	Value
Size	4 bytes (32 bits)
Precision	About 7 significant digits
Largest value	`3.4028235E38`
Smallest positive value	`1.4E-45`
Default value (fields)	`0.0f`
Literal suffix	`f` or `F`
Wrapper class	`Float`

float vs double

Feature	`float`	`double`
Size	4 bytes	8 bytes
Precision	About 7 digits	About 15 to 16 digits
Suffix needed	Yes (`f`)	No (default for decimals)
Best for	Large arrays, graphics, saving memory	Most general calculations

Output

a = 234.5
b = 234.565
pi = 3.1415927
Max float value = 3.4028235E38
Min float value = 1.4E-45

Common Mistakes

Missing the f suffix float a = 234.5; gives the error incompatible types: possible lossy conversion from double to float.

Using float for money float can't store most decimal values exactly, so small rounding errors appear. Use BigDecimal for currency.

Thinking MIN_VALUE is negative Float.MIN_VALUE is the smallest positive value. The most negative float is -Float.MAX_VALUE.

Good practice Use double by default for decimal numbers, and use float only when memory matters or an API requires it.

Key Takeaway

float stores decimal numbers in 4 bytes with about 7 digits of precision. Always add the f suffix to float literals, and use double when you need more precision

Complexity

Time: O(1)

Space: O(1)

🎯 How to learn from this example

First understand the algorithm carefully. Then study the program line-by-line and compare it with the output. Finally, review the explanation section to strengthen your logic and programming understanding.

🔥 Practice suggestion

Rewrite the program without looking at the code. Modify values, conditions or logic and run it again. This helps improve confidence and strengthens coding skills much faster.