La récursivité en Java est un processus dans lequel une méthode s'appelle en continu. Une méthode en Java qui s'appelle elle-même est appelée méthode récursive.
Cela rend le code compact mais complexe à comprendre.
Syntaxe:
returntype methodname(){ //code to be executed methodname();//calling same method } Exemple de récursion Java 1 : temps infinis
public class RecursionExample1 { static void p(){ System.out.println('hello'); p(); } public static void main(String[] args) { p(); } } Sortir:
hello hello ... java.lang.StackOverflowError
Exemple de récursion Java 2 : temps finis
public class RecursionExample2 { static int count=0; static void p(){ count++; if(count<=5){ system.out.println('hello '+count); p(); } public static void main(string[] args) { < pre> <p>Output:</p> <pre> hello 1 hello 2 hello 3 hello 4 hello 5 </pre> <h2>Java Recursion Example 3: Factorial Number</h2> <pre> public class RecursionExample3 { static int factorial(int n){ if (n == 1) return 1; else return(n * factorial(n-1)); } public static void main(String[] args) { System.out.println('Factorial of 5 is: '+factorial(5)); } } </pre> <p>Output:</p> <pre> Factorial of 5 is: 120 </pre> <p> <strong>Working of above program:</strong> </p> <pre> factorial(5) factorial(4) factorial(3) factorial(2) factorial(1) return 1 return 2*1 = 2 return 3*2 = 6 return 4*6 = 24 return 5*24 = 120 </pre> <h2>Java Recursion Example 4: Fibonacci Series</h2> <pre> public class RecursionExample4 { static int n1=0,n2=1,n3=0; static void printFibo(int count){ if(count>0){ n3 = n1 + n2; n1 = n2; n2 = n3; System.out.print(' '+n3); printFibo(count-1); } } public static void main(String[] args) { int count=15; System.out.print(n1+' '+n2);//printing 0 and 1 printFibo(count-2);//n-2 because 2 numbers are already printed } } </pre> <p>Output:</p> <pre> 0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 </pre></=5){> Exemple de récursion Java 3 : nombre factoriel
public class RecursionExample3 { static int factorial(int n){ if (n == 1) return 1; else return(n * factorial(n-1)); } public static void main(String[] args) { System.out.println('Factorial of 5 is: '+factorial(5)); } } Sortir:
Factorial of 5 is: 120
Fonctionnement du programme ci-dessus :
factorial(5) factorial(4) factorial(3) factorial(2) factorial(1) return 1 return 2*1 = 2 return 3*2 = 6 return 4*6 = 24 return 5*24 = 120
Exemple de récursion Java 4 : série de Fibonacci
public class RecursionExample4 { static int n1=0,n2=1,n3=0; static void printFibo(int count){ if(count>0){ n3 = n1 + n2; n1 = n2; n2 = n3; System.out.print(' '+n3); printFibo(count-1); } } public static void main(String[] args) { int count=15; System.out.print(n1+' '+n2);//printing 0 and 1 printFibo(count-2);//n-2 because 2 numbers are already printed } } Sortir:
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377