Creating Our Own Methods

How to use methods?

In the previous chapter, we looked at creating a method that adds two numbers. Now let's see how we can actually call this method in our code:

Main


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package com.example;

public class Main {
    public static void main(String[] args) {
        int a = 10;
        int b = 31;
        // here we are using our method to add two numbers - "a" and "b"
        int sum = addTwoNumbers(a, b);
        System.out.println(sum);
    }

    static int addTwoNumbers(int firstNumber, int secondNumber) {
       int result = firstNumber + secondNumber;
       return result;
    }
}

Note
You may have noticed that we added static before the method signature. For now, you don't need to pay attention to this keyword. We are using it only because the main method is static by default, and static methods can only use other static methods within them.

We created two variables of type int with different values and then passed them as parameters to our method;
Since our method returns an int type, we can initialize the variable sum with the result of calling the method;
Thus, our method calculated and returned the sum of the two numbers.

We can also pass arrays as parameters and return them from methods. Let's look at an example:

Main


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package com.example;

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        // creating unsorted array
        int[] array = {4, -1, 5, 0, 4, -6, 2, 7, 4, 1};
        // using method to sort and increment every element
        int[] newArray = sortAndIncrementEveryElement(array);
        // printing our new array
        for (int element : newArray) {
            System.out.print(element + " ");
        }
    }

    static int[] sortAndIncrementEveryElement(int[] inputArray) {
        // creating a result array 
        int[] result = new int[inputArray.length];
        // incrementing every element by 1
        for (int i = 0; i < inputArray.length; i++) {
            result[i] = inputArray[i] + 1;
        }
        // sorting our result array
        Arrays.sort(result);
        // returning sorted and incremented array
        return result;
    }
}

We have written a method that sorts and increments each element of an integer array (int[]). Then we create an unsorted array and use the method on it, initializing a new array called newArray with the returned value.

It is worth noting that we can use this method multiple times in the same code, for example:

Main


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package com.example;

import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        // creating unsorted arrays
        int[] array = {4, -1, 5, 0, 4, -6, 2, 7, 4, 1};
        int[] secondArray = {2, 2, 0, -5, 1, 8, 13, -9, 0};
        // using method to sort and increment every element
        int[] newArray = sortAndIncrementEveryElement(array);
        int[] newSecondArray = sortAndIncrementEveryElement(secondArray);
        // printing our new arrays
        for (int element : newArray) {
            System.out.print(element + " ");
        }
        System.out.println(System.lineSeparator());
        for (int element : newSecondArray) {
            System.out.print(element + " ");
        }
    }

    static int[] sortAndIncrementEveryElement(int[] inputArray) {
        // creating a result array
        int[] result = new int[inputArray.length];
        // incrementing every element by 1
        for (int i = 0; i < inputArray.length; i++) {
            result[i] = inputArray[i] + 1;
        }
        // sorting our result array
        Arrays.sort(result);
        // returning sorted and incremented array
        return result;
    }
}

Thus, we can see that we can use our method multiple times in the code. We have used it on two different integer arrays, and each of them is now sorted and incremented.

Tudo estava claro?

Obrigado pelo seu feedback!

Seção 2. Capítulo 2