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Program a Java factorial function with recursion and iteration

6 min read

The factorial of 5 is 120.
The factorial of 10 is 3,628,800.

Programmers can take one among two approaches after they develop an answer to the Java factorial drawback. The can take an iterative method, or they’ll write a program that does Java factorial recursion.

For individuals who aren’t math wizards, the factorial of a quantity is the entire entire numbers that precede it multiplied collectively. The quantity itself can also be included within the multiplication. So 10 factorial, additionally written as 10!, is:

1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 10 = 3,628,800.

5 factorial, additionally written as 5! is:

1 x 2 x 3 x 4 x 5 = 120.

Since these calculations use each integer in a collection of numbers, they lend themselves nicely to Java coaching workout routines, because the properly reveal loops and iterative buildings. In addition they present a possibility to distinction iterative vs recursive Java algorithms.

Iterative Java factorial capabilities

Right here’s an iterative Java factorial program that calcuates 10!.

bundle com.mcnz.recursion;
/* Calculate a factorial with out recursion in Java. */
public class IterativeJavaFactorialProgram {

  public static void major(String[] args) {
    int factorialProduct = 1;

    for(int i=1; i<=5; i++) {
      factorialProduct = factorialProduct * i;

  System.out.println("n Iterative Java factorial end result: " + factorialProduct);

Output from iterative Java factorial code:
 Iterative Java factorial end result:

Recursive Java factorial code

Let’s distinction the iterative method with a Java program to search out factorials utilizing recursion.

bundle com.mcnz.recursion;

public class RecursiveJavaFactorialProgram {

  public static void major(String args[]) {
    /* Recursive Java factorial operate. */
    lengthy nFactoriral = factorialFunction(5);

  /* Java factorial recursive technique. */
  public static lengthy factorialFunction(lengthy n) {
    if (n <= 1) {
      return 1;
    } else {
      return n * factorialFunction(n - 1);

Java factorial recursion defined

Discover how the recursive Java factorial operate doesn’t want an iterative loop. As a substitute, the code repeatedly calls itself till a situation is met. On this case, the situation to terminate the Java factorial recursion is when the quantity handed into the factorialFunction technique is lower than or equal to at least one. The code then terminates, printing out the factorial of the given quantity.

Many junior builders just like the recursive method to drawback fixing. Others discover this method tough to conceptualize. The next sequence that describes the computation course of used the Java factorial recursion would possibly assist simplify issues.

The recursive Java factorial operate stacks technique calls on high of one another.

When the recursive Java factorial program runs, it creates a stack of technique calls that seem like this:


When the situation that marks the top of recursion is met, the stack is then unraveled from the underside to the highest, so factorialFunction(1) is evaluated first, and factorialFunction(5) is evaluated final. The order during which the recursive factorial capabilities are calculated turns into:


The result’s 120.

Iterative vs recursive factorial capabilities

Word that with an iterative loop, strategies calls aren’t stacked on high of one another. This eliminates the potential for a StackOverflowError to be thrown when loops are used. In distinction, the potential of a StackOverflowError looms just like the sword of Damocles each time you utilize Java recursion. A lot of stack frames can crash the JVM.

Moreover, iterative loops enable for linear processing, which on the JVM, is quicker than the exponential processing charges related to Java recursion. If Java efficiency is vital, recursion is finest averted.

Many platforms optimize recursive operate calls, however the JVM is just not one among them.

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