CheckLeapYear()

Step 1: Understand the Problem

The first step in writing the function for checking a leap year in Java is to understand the problem. A leap year is a year that is exactly divisible by 4 except for end of century years which must be divisible by 400. This means that the year 2000 was a leap year although 1900 was not.

To implement this, you need a function that accepts a year as an input and then checks the following conditions:

1. If the year is divisible by 4 and not divisible by 100, it is a leap year.
2. If it is also divisible by 400, then it is still a leap year.

public boolean checkLeapYear(int year) {
    // Initial step: Check if year is divisible by 4
    if(year % 4 == 0) {
        // Further steps will be added in the next steps
    }
}

Step 2: Handle Non-Century Year

The next step is to handle the condition of non-century years. According to the leap year rules, all non-century years which are divisible by 4 are leap years.

public boolean checkLeapYear(int year) {
    if(year % 4 == 0) {
        if(year % 100 != 0) {
            // If year is not a century year, it is a leap year
            return true;
        }
    }
}

Step 3: Handle Century Years

The next step is to add handling for century years. Century years that are exactly divisible by 400 are leap years.

public boolean checkLeapYear(int year) {
    if(year % 4 == 0) {
        if(year % 100 != 0) {
            return true;
        } else if(year % 400 == 0) {
            // If year is a century year and is divisible by 400, it is a leap year
            return true;
        }
    }
}

Step 4: Non-Leap Year Condition

If none of the above conditions are met, that means the year is not a leap year. So, return false.

public boolean checkLeapYear(int year) {
    if(year % 4 == 0) {
        if(year % 100 != 0) {
            return true;
        } else if(year % 400 == 0) {
            return true;
        }
    }
    return false;
}

Step 5: Test the Function

The final step is to test your function with different inputs to ensure it is working correctly.

public static void main(String[] args) {
    System.out.println(checkLeapYear(2000));  // Output: true
    System.out.println(checkLeapYear(1900));  // Output: false
    System.out.println(checkLeapYear(2020));  // Output: true
    System.out.println(checkLeapYear(2021));  // Output: false
}

In the conclusion, this function successfully checks if a given year is a leap year or not using Java.