What are the uses of final keyword in java

The final keyword in Java has the following three uses: Declare constants and ensure that they cannot be modified. Improve code safety by decorating classes, methods, and variables so they cannot be inherited, overridden, or reassigned. Using final when declaring local variables in a method or constructor prevents Null Pointer Exceptions because it initializes the variable or gives it a default value at compile time.

Usage of final keyword in Java

The final keyword in Java is A powerful modifier widely used to ensure code safety and correctness. It has three main uses:

1. Declare constants

final is used to declare constants that cannot be reassigned or modified. Constants are usually represented by uppercase characters, for example:

<code class="java">final int MAX_VALUE = 100;</code>

2. Modify classes, methods and variables

final can modify classes, methods and variables , which means they cannot be inherited, overridden, or reassigned.

• final class: Cannot be inherited, preventing subclasses from modifying or extending its behavior.
• final method: cannot be overridden, ensuring that the behavior of the method is consistent.
• final variable: is not reassignable and once initialized, its value will remain unchanged.

3. Prevent null pointer exceptions

Use the final keyword when declaring local variables in a method or constructor to prevent Null pointer exception. final Variables will be initialized at compile time. If not explicitly initialized, they will be automatically assigned a default value.

For example, the following code may cause a null pointer exception:

<code class="java">public void greet(String name) {
    if (name == null) {
        System.out.println("Hello, null!");
    } else {
        System.out.println("Hello, " + name + "!");
    }
}</code>

This can be avoided by using the final keyword:

<code class="java">public void greet(final String name) {
    if (name == null) {
        System.out.println("Hello, null!");
    } else {
        System.out.println("Hello, " + name + "!");
    }
}</code>

Here In this case, the compiler will detect that the name variable is not initialized at compile time and issue a warning or error.

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