Java Double longValue Method

Introduction

In this lab, you will learn how to use the longValue() method of the Double class in Java to convert a Double number to its long equivalent. You will also learn how to implement this method through examples.

Skills Graph

Create a new Java file

• Navigate to the terminal and create a new Java file by executing:

touch DoubleLong.java

• Open the file with your preferred text editor by executing:

code DoubleLong.java

Declare a Double number

• In the main() method of the DoubleLong class, declare and initialize a Double number.

Double num = 654.987;

Convert the Double number to its long equivalent using longValue()

• Call the longValue() method on the num object to convert it to its long equivalent.

long longNum = num.longValue();

Print the long equivalent of the Double number

• Print the long equivalent of the Double number using System.out.println().

System.out.println("Long equivalent: " + longNum);

Compile and run the program

• On the terminal, compile the DoubleLong.java file by running the command:

javac DoubleLong.java

• Run the program using the command:

java DoubleLong

• The output should display the long equivalent of the Double number.

Test with different values

• Declare and initialize different Double numbers in the main() method.

Double num1 = 123.456;
Double num2 = 987.654;

• Call the longValue() method and print the long equivalent of each Double number.

long longNum1 = num1.longValue();
System.out.println("Long equivalent of num1: " + longNum1);
long longNum2 = num2.longValue();
System.out.println("Long equivalent of num2: " + longNum2);

• Compile and run the program to see the long equivalent of the new Double numbers.

Use user input

• Add a user input section to your code that prompts the user to enter a Double number via the terminal.

Scanner sc = new Scanner(System.in);
System.out.print("Enter a double number: ");
Double input = sc.nextDouble();

• Convert the user's Double input to its long equivalent and print the result.

long longInput = input.longValue();
System.out.println("Long equivalent of input: " + longInput);

• Compile and run the program, and test with different input values.

Add exception handling

• Surround the user input section with a try-catch block to handle exceptions.

try {
   Scanner sc = new Scanner(System.in);
   System.out.print("Enter a double number: ");
   Double input = sc.nextDouble();
   long longInput = input.longValue();
   System.out.println("Long equivalent of input: " + longInput);
} catch (Exception e) {
   System.out.println("Invalid input. Please enter a valid double number.");
}

• Compile and run the program, and test with different input values.

Implement method chaining

• Implement method chaining to chain the longValue() method to the Double object creation.

Double num = Double.valueOf(321.654).longValue();

• Print the long equivalent of the num object.

System.out.println("Long equivalent of num: " + num);

• Compile and run the program to see the output.

Finalize the code

- Finalize the code by closing the scanner object and the main method.
```java
sc.close();
}
```

Summary

Congratulations! You have successfully learned to use the longValue() method of the Double class in Java to convert a Double number to its long equivalent. In this lab, you have covered the following:

• How to declare and initialize a Double number
• How to convert a Double number to its long equivalent using longValue()
• How to print the long equivalent of a Double number
• How to implement user input and exception handling
• How to implement method chaining.

Use these steps as a reference to implement this concept in your Java programs. Happy learning!