Recursion in java is a process in which a method calls itself continuously. A method in java that calls itself is called recursive method.
It makes the code compact but complex to understand.
Syntax:
returntype methodname(){
//code to be executed
methodname();//calling same method
}Java Recursion Example 1: Infinite times
public class RecursionExample1 {
static void p(){
System.out.println("hello");
p();
}
public static void main(String[] args) {
p();
}
}Output:
hello
hello
...
java.lang.StackOverflowError
Java Recursion Example 2: Finite times
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) {
p();
}
} Output:
hello 1
hello 2
hello 3
hello 4
hello 5
Java Recursion Example 3: Factorial Number
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));
}
} Output:
Factorial of 5 is: 120
Working of above program:
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
Java Recursion Example 4: Fibonacci Series
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
}
} Output:
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377
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