final keyword in java explained in 2 mins

In Java, final is an access modifier. It could be used to modify:

final for class

class: this means the class cannot be inherited by subclasses.

public final class Dog extends Animal
{
    // code
}

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final for method

method: this means the method cannot be overwritten by subclasses. Use this if you want this method to be non-modifiable by subclasses.

public class Aminal 
{
    // other code
    public final eat() {
        // code
    }
}

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final for variable

variable: this means the variable can only be assigned once. Use this when you want a constant variable. Typical usage is like

final double PI = 3.14159;

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Also, we remark that Math.PI is a built-in constant variable declared using final. Math is a build-in final class that cannot be inherited.

A peek to the Math class:

public final class Math {

    /** * Don't let anyone instantiate this class. */
    private Math() {}

    /** * The {@code double} value that is closer than any other to * <i>e</i>, the base of the natural logarithms. */
    public static final double E = 2.7182818284590452354;

    /** * The {@code double} value that is closer than any other to * <i>pi</i>, the ratio of the circumference of a circle to its * diameter. */
    public static final double PI = 3.14159265358979323846;
// ... other code ... 

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reference

code with John

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