Understanding Java as a Strongly Typed Language: A Beginner’s Guide

In programming, languages can be classified as either strongly typed or loosely typed, based on how they handle data types. If you've been working with languages like JavaScript, you might have noticed that variable types aren’t strictly enforced. However, Java works quite differently—it’s a strongly typed language, meaning that data types must be explicitly declared and conversion between incompatible types isn’t allowed.

In this post, I’ll break down two key concepts that illustrate Java’s strong typing and show you why these features can help you write safer, more reliable code.

Concept 1: No Automatic Type Coercion

Java doesn’t allow automatic type coercion. This means that the data type for each variable must be specified explicitly by the programmer, and any attempt to assign a value of a different type to a variable will result in a compile-time error.

Example:

package basics;

public class StronglyTypedLanguage {

    public static void main(String[] args) {

        // This will result in compilation error
        // Error: number cannot be resolved to a variable
        number = 10;

        int num = 10; // Correct Usage

        // This will result in compilation error
        // Error: Cannot implicitly convert from int to String
        num = "Hello";
    }
}

In the above code:

• If you try to assign a value to number without declaring its type, Java won’t compile the program.

• Java also won’t implicitly convert "Hello" (a string) to an int type, unlike loosely typed languages where this kind of behavior is allowed or coerced.

This strict enforcement of data types helps catch bugs early during the development process, before the code even runs. For example, assigning a string to an integer variable could lead to unexpected errors at runtime in other languages, but Java’s strong typing eliminates that risk.

Concept 2: No Hoisting – Variables Must Be Declared Before Use

Another concept in Java’s type system is that variables must be declared before they are used. This is in contrast to languages like JavaScript, where variables can be hoisted (used before declaration).

Example:

package basics;

public class StronglyTypedLanguage {

    public static void main(String[] args) {

        // This will result in compilation error
        // Error: num cannot be resolved to a variable
        num = 20; // Initializing first
        int num; // Declaration later

        int number = 20; // Correct Usage
    }
}

In this example:

• The variable num must be declared with a type (int) before assigning it a value (20). If you attempt to assign a value without declaring the variable first, the code won’t compile.

This ensures that you always know the type of each variable before you use it, preventing hard-to-find bugs caused by undefined or undeclared variables.

Why Strong Typing Matters

Strong typing helps you write more robust and maintainable code. By requiring explicit declarations and preventing type coercion, Java ensures that:

• Type-related errors are caught early during compile-time, saving you from the hassle of debugging at runtime.

• You are less likely to encounter unexpected behavior caused by automatic type conversions.

• The code is self-documenting. When reading the code, you know exactly what kind of data each variable holds, improving code readability and maintainability.

In large-scale applications, this extra level of discipline can significantly reduce bugs and make the codebase easier to understand and manage.

Conclusion

Java’s strong typing might seem rigid at first, but it plays a crucial role in building stable and reliable applications. By enforcing strict rules around variable declaration and data types, Java helps you catch potential bugs at compile time, giving you more confidence in your code.

If you’re interested in more insights into Java fundamentals, be sure to check out my other posts in this series.

You can also check out my Array Interview Essentials series, which includes fundamental concepts and interview preparation, along with more details on Java nuances.

Happy coding!