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Recursive Methods in Java
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In Java, methods can call themselves; this is called recursion and is an efficient and elegant way of working with methods. Recursive methods in Java facilitate and structure our work in larger programs.
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What is Recursive Methods in Java?
A recursive method in Java is a method that is defined by having references to itself; that is, the method calls itself. Using recursive methods is a common programming technique that can create a more efficient and more elegant code. Further, a recursive method always contains a base condition, also called the trivial case, which indicates the end of the recursion and which therefore does not call itself.
A recursive method in Java is a method that calls itself
Recursive methods in Java,
- is a reference to itself
- always contains a base condition
- can handle direct and indirect calls
- commonly used in programming and mathematics.
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Base Condition, Direct- and Indirect recursion
Some terms that are good to be familiar with when working with recursive methods are:
- Base condition: A recursive method must always have a base case. The base condition is the trivial case that indicates when the recursion is complete.
- Direct Recursion: A method that calls itself.
- Indirect call: A method that calls another method, which in turn calls the first method again. Note that indirect calls, for this reason, is often difficult to get an overview.
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Example – Declaring a Recursive method in Java
Let´s declare a recursive method that sums all the integers between 1 and N.
- First, we check the base condition, that is, if N is equal to one. In this case, there is no need to call the method again. Therefore, the recursion will not be needed in this case.
- However, if N is greater than N, the method will call itself until all we summed all the integers.
private static int summa (int N) {
// Support variable
int sum;
// Base condition
if (N == 1) {
sum = 1;
}
else {
//The method calls itself -> Recursive call
sum = N + summa(N - 1);
}
return sum;
}
The code above provides the following case,
public static void main(String[] args) {
// Print the sum of all integers between 1 and 4
System.out.println(summa(4));
// Print the sum of all integers between 1 and 10
System.out.println(summa(10));
// Base condition
System.out.println(summa(1));
}
Resulting in,
10 55 1
Moreover, the image below is an illustration of how the method works when N = 3.[/vc_column_text][vc_empty_space height=”30px”][vc_single_image image=”20169″ img_size=”large” alignment=”center” onclick=”link_image” qode_css_animation=””][vc_empty_space height=”30px”][vc_column_text]
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