By using parent reference, we can call only methods available in parent class and we can't call child specific methods.
we can use parent reference to hold any child class object.

class Parent {
    int duplicateVariable = 10;
    String parentString = "parent string value";

    Parent() {
        System.out.println("parent Constructor");
    }

    public void duplicate_method() {
        System.out.println("duplicate method in Parent class");
    }

    public void parentMethod() {
        System.out.println("Parent method");
    }
}

class Child extends Parent {
    int duplicateVariable = 20;
    String childString = "child string value";

    Child() {
        System.out.println("child Constructor");
    }

    public void duplicate_method() {
        System.out.println("duplicate method in child class");
    }

    public void childMethod() {
        System.out.println("child method");
    }
}

public class ParentChildProgram {
    public static void main(String[] args) {
    Parent parentObj = new Child();
    System.out.println("Value=" + parentObj.duplicateVariable);// variable in parent class invoked
    parentObj.duplicate_method();// duplicate method in child class is invoked
    parentObj.parentMethod();
    System.out.println(parentObj.parentString);
  }
}

Output:


Parent p=new Child()

If we use parent reference to call specific child class specific methods we will get compile time error like below:


Parent P = new Child() compile time error

Child c=new Child() ?

By using child reference we can call both parent and class methods.
We can use child reference to hold only for that particular child class object only.

class Parent {
    int duplicateVariable = 10;
    String parentString = "parent string value";

    Parent() {
        System.out.println("parent Constructor");
    }

    public void duplicate_method() {
        System.out.println("duplicate method in Parent class");
    }

    public void parentMethod() {
        System.out.println("Parent method");
    }
}
class Child extends Parent {
    int duplicateVariable = 20;
    String childString = "child string value";

    Child() {
        System.out.println("child Constructor");
    }

    public void duplicate_method() {
        System.out.println("duplicate method in child class");
    }

    public void childMethod() {
        System.out.println("child method");
    }
}
public class ParentChildProgram {
    public static void main(String[] args) {
    Child childObj = new Child();
    System.out.println("Value=" + childObj.duplicateVariable);// variable in child class invoked
    childObj.duplicate_method();// duplicate method in child class is invoked
    childObj.parentMethod();
    childObj.childMethod();
    System.out.println(childObj.parentString);
    System.out.println(childObj.childString);
  }
}

Output:
Child c=new Child()

Please comment below to feedback or ask questions.

java8 features

Java 8 features

Below are new features that are introduced in Java 8 :

Lambda expression
Functional Interface
Default Methods and static methods
Predefined Functional interfaces (Predicate, Functional, Consumer, supplier, etc.,.)
Double colon operator(::), Method reference, constructor reference
Streams
Date and Time API
Optional class
nashorn JavaScript engine
StringJoiner
Collectors class etc.,.

Lambda expression::

It is an anonymous function i.e., a lambda expression is Nameless, without return type, without modifiers.
It brings the benefits of functional programming into Java.
Lambda expression can implement an interface that contains a Single Abstract Method(SAM.)
Click here for details

Functional Interface::

Interface which contains SAM(Single Abstract Method) is called Functional Interface
It also contains Any number of default methods and static methods
In order to invoke lambda expression, we require a Functional Interface.

Default Methods:

Until Java 1.7, Every method present inside the interface is always public and abstract
In Java 1.8V, default methods and static methods are allowed
In Java 1.9V, private methods are allowed

Static Methods:

From Java 1.8, the interface can contain static methods.
We should call static methods in the interface by using its interface name only.
static methods in an interface are by default not available to implementation classes. So we have to call by using interface name only.

Verify the display of element which disappear immediately in protractor

Verify the display of element which disappear immediately in protractor ?

describe('Protractor - Verify the display of element which disappear immediately in protractor', function () {
    beforeAll(async function () {
        await browser.get("https://keeplearners.blogspot.com/2018/03/Angular-elements.html");
    });

    it('Verify the display of element which disappear immediately in protractor', async function () {
        verifyBlinkMessage(2000, 0, "className");
    });

    function verifyBlinkMessage(totalCount, currentCount, className) {
        if (currentCount < totalCount) {
            return browser.executeScript("return document.getElementsByClassName('" + className + "').length").then(function (value) {
                if (value > 0) {
                    console.log("Element displayed=" + value);
                    return browser.executeScript("return document.getElementsByClassName('" + className + "')[0].innerText").then(function (textPopUp) {
                        console.log("pop up message=" + textPopUp);
                        return textPopUp;
                        // return true;
                    });
                } else {
                    console.log("Page is loading....");
                    return verifyBlinkMessage(totalCount, currentCount++, className);
                }
            });
        } else {
            throw new Error("element not present after Max count" + totalCount + "ms reached.")
            // return false; //if element not present after Max count reached.
        }
    }
});



Please comment below to feedback or ask questions.

Sum of individual digits of a number

Sum of individual digits of a number

We can find the sum of individual digits of a given number using loop , java 8 etc.,.

public class SumOfDigits {
    public static void main(String[] args) {
        int number = 111111;
        int p;
        int sum = 0;
        while (number != 0) {
            p = number % 10;
            sum = sum + p;
            number = number / 10;
        }
        System.out.println("sum of individual digits of given number=" + sum);

        int n = 123;

    //sum of individual digits of given number using java 8
    int sumOfDigits = String.valueOf(n).chars().map(Character::getNumericValue).sum();
    System.out.println("sum of individual digits of given number using map=" + sumOfDigits);
   }
}

Output:
Sum of individual digits of a number
Please comment below to feedback or ask questions.

valueOf() in java ?

valueOf() in Java ?

valueOf() method will convert any type(int,float,char etc.,.) of data into a string.

##Demo program on valueOf()###

public class valueOf {
    public static void main(String[] args) {
    int i = 10;
    System.out.println(i + 20);
    String IntTostr = String.valueOf(i);
    System.out.println(IntTostr + 20);
    System.out.println("Type=" + IntTostr.getClass());
    System.out.println("<<---------------------------------------->>");
    boolean v = false;
    String BooleanTostr = String.valueOf(v);
    System.out.println("boolean to string=" + BooleanTostr);
    System.out.println("Type=" + BooleanTostr.getClass());
    System.out.println("<<---------------------------------------->>");
    char c = 'L';
    String CharTostr = String.valueOf(c);
    System.out.println("char to string=" + CharTostr);
    System.out.println("Type=" + CharTostr.getClass());
    System.out.println("<<---------------------------------------->>");
    float f = 10.2f;
    String floatTostr = String.valueOf(f);
    System.out.println("float to string=" + floatTostr);
    System.out.println("Type=" + floatTostr.getClass());

    System.out.println("<<---------------------------------------->>");
    char[] carr = { 'A', 'B', 'C', 'D' };
    String charArrToStr = String.valueOf(carr);
    System.out.println("char array to string=" + charArrToStr);
    System.out.println("Type=" + charArrToStr.getClass());

    System.out.println("<<---------------------------------------->>");
    Object o=12;
    String objectTostr = String.valueOf(o);
    System.out.println("Object to string=" + objectTostr);
    System.out.println("Type=" + objectTostr.getClass());
  }
}

Output:


valueOf() in java
Please comment below to feedback or ask questions.

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Contents

Parent p=new Child() parent and child object reference in java

java8 features

Verify the display of element which disappear immediately in protractor

Verify the display of element which disappear immediately in protractor ?

Sum of individual digits of a number

valueOf() in java ?

valueOf() in Java ?

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