FinalKeywordExample.java

package Phase1_CoreLanguage.SpecialKeyword;

/**A final variable in Java can be assigned a value only once, we can assign a value either in declaration or later.
 *     final int i = 10;
 *     i = 30; // Error because i is final.
 * <p>
 *
 *blank final variable in Java is a final variable that is not initialized during declaration. Below is a simple example of blank final.
 * <p>
 *
 *     // A simple blank final example
 *     final int i;
 *     i = 30;
 * <p>
 *
 *     **/

//How are values assigned to blank final members of objects?
//Values must be assigned in constructor.

// A sample Java program to demonstrate use and
// working of blank final
class Test
{
    // We can initialize here, but if we
    // initialize here, then all objects get
    // the same value.  So we use blank final
    final int i;

    Test(int x)
    {
        // Since we have initialized above, we
        // must initialize i in constructor.
        // If we remove this line, we get compiler
        // error.
        i = x;
    }
}

// Driver Code
class FinalKeywordExample
{
    public static void main(String args[])
    {
        Test t1 = new Test(10);
        System.out.println(t1.i);

        Test t2 = new Test(20);
        System.out.println(t2.i);
    }

    //OUTPUT
    //10
    //20
}


//If we have more than one constructors or overloaded constructor in class, then blank final variable must be initialized in all of them.
// However constructor chaining can be used to initialize the blank final variable.

// A Java program to demonstrate that we can
// use constructor chaining to initialize
// final members
class Test2
{
    final public int i;

    Test2(int val) {
        this.i = val;
    }

    Test2()
    {
        // Calling Test(int val)
        this(10);
    }

    public static void main(String[] args)
    {
        Test2 t1 = new Test2();
        System.out.println(t1.i);

        Test2 t2 = new Test2(20);
        System.out.println(t2.i);
    }
}