Method Overloading

Using a method with different parameters

Java allows us to write different methods with the same name. These methods can have different return types and/or parameter types. This is done so that we can use these methods with different types. Let's take the example of a method to print an array:

We can write this method to accept values of type int, but what if we need to print an array of type char? Do we have to write a method with a different name?

Java provides method overloading for this purpose.

Let's take a look at an example of printing data and reversing an array from the previous chapter:

Main


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// method to reverse an int array
static int[] flipArray(int[] array) {
    // creating a new array to store the reversed elements
    int[] result = new int[array.length];
    int index = 0;
    // iterating over the input array in reverse order
    for (int i = array.length - 1; i > 0; i--) {
        result[index] = array[i];
        index++;
    }
    // returning the reversed int array
    return result;
}

// method to reverse a char array
static char[] flipArray(char[] array) {
    // creating a new array to store the reversed elements
    char[] result = new char[array.length];
    int index = 0;
    // iterating over the input array in reverse order
    for (int i = array.length - 1; i >= 0; i--) {
        result[index] = array[i];
        index++;
    }
    // returning the reversed char array
    return result;
}

We overloaded the method flipArray to accept and return different parameters: int and char. If we invoke this method, it can accept and return both int and char types.

Now let's overload the method to display an array on the screen. This method should also accept and return int and char types:

Main


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// method to print an int array
static void printArrayToTheConsole(int[] array) {
    // iterating through each element of the int array
    for (int element : array) {
        System.out.print(element + " ");
    }
    // printing a blank line after the array
    System.out.println();
}

// method to print a char array
static void printArrayToTheConsole(char[] array) {
    // iterating through each element of the char array
    for (char element : array) {
        System.out.print(element + " ");
    }
    // printing a blank line after the array
    System.out.println();
}

Here we have overloaded the method printArrayToTheConsole to accept and return int and char values.

Now let's combine the overloaded methods and use them in the main method for an array of int type and an array of char type:

Main


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package com.example;

public class Main {
    // main method to run the application
    public static void main(String[] args) {
        // do not modify the code below
        int[] intArray = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        char[] charArray = {'s', 'b', 'c', 'd', 'e', 'f', 'g'};
        printArrayToTheConsole(flipArray(intArray));
        printArrayToTheConsole(flipArray(charArray));
    }

    // method to reverse an int array
    static int[] flipArray(int[] array) {
        int[] result = new int[array.length];
        int index = 0;
        // iterating over the array in reverse order
        for (int i = array.length - 1; i > 0; i--) {
            result[index] = array[i];
            index++;
        }
        return result;
    }

    // method to reverse a char array
    static char[] flipArray(char[] array) {
        char[] result = new char[array.length];
        int index = 0;
        // iterating over the array in reverse order
        for (int i = array.length - 1; i >= 0; i--) {
            result[index] = array[i];
            index++;
        }
        return result;
    }

    // method to print an int array to the console
    static void printArrayToTheConsole(int[] array) {
        // printing each element of the int array
        for (int element : array) {
            System.out.print(element + " ");
        }
        System.out.println();
    }

    // method to print a char array to the console
    static void printArrayToTheConsole(char[] array) {
        // printing each element of the char array
        for (char element : array) {
            System.out.print(element + " ");
        }
        System.out.println();
    }
}

We have overloaded two different methods by adding the ability to use these methods with arrays of type char. We have also slightly changed the names of these methods, as now we can overload them multiple times to accept and return values of different types.

To verify this, we created two different arrays, one of type int and the other of type char, and then passed these arrays to the overloaded methods, obtaining the correct results.

By the way, you have already encountered overloaded methods before. For example, the String method substring() is overloaded and can have either one parameter, int beginIndex, or two parameters, int beginIndex, int endIndex. Method overloading is very useful and is commonly used in practice.

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Seção 2. Capítulo 6