Choosing the correct data type improves performance, prevents errors, and makes your program more reliable.

When to Use int vs long

Use int when:

The number is within range of -2,147,483,648 to 2,147,483,647
You are working with normal counters, loops, indexes

Example:

Use long when:

The number is very large
You are working with population data, bank account numbers, timestamps

Example:

If you try to store a very large value in int, it will cause overflow.

When to Use float vs double

Use float when:

Memory is limited
You are working with large arrays of decimal values
High precision is not required

Example:

Use double when:

Precision matters
Performing scientific calculations
Working with financial or mathematical values

Example:

Why double is Preferred

Higher precision than float
Default type for decimal numbers
Less rounding error
Better for calculations

Example showing precision difference:

You will notice double retains more precision.

In real world Java development, double is commonly preferred over float.

Code Challenge

1. Identify Correct Data Type

Choose correct data types for the following:

Age of a person
Price of a product
Whether a user is logged in
First letter of a name

Correct example:

2. Fix Errors

Find and fix errors in the following code.

Incorrect code:

Corrected version:

3. Output Prediction

Predict the output before running.

Explanation:

int is automatically converted to double
10 becomes 10.0
Result becomes 15.5

Output:

These best practices and challenges strengthen understanding of Java data types and help build strong logical thinking for real programming scenarios.