Removing white spaces

Method 1:
String s = "This is a sentence";
String s2 = s.trim();


Method 2:
String s = "This is a sentence";
String s2 = s.replaceAll("\\s", "");

Find Factorial of a number

public static int factorial(int number){
//base case
if(number == 0){
return 1;
}
return number*factorial(number -1);
}

(OR)

public static int factorial(int number){
int result = 1;
while(number != 0){
result = result*number;
number--;
}

return result;
}
}

Print Fibonacci Series

public static int fibonacci2(int number)

{

 if(number == 1 || number == 2)

{ return 1; }

 int fibo1=1, fibo2=1, fibonacci=1; 

for(int i= 3; i<= number; i++)

{ 

 fibonacci = fibo1 + fibo2;  //Fibonacci number is sum of previous two Fibonacci number 

 fibo1 = fibo2;

 fibo2 = fibonacci; 

}

 return fibonacci; //Fibonacci number 

}

}

(OR)

public static int fibonacci(int number)

{

 if(number == 1 || number == 2)

{ return 1; } 

return fibonacci(number-1) + fibonacci(number -2); //tail recursion 

}

Check if String Palindrome

We can check palindrome string by reversing string and checking whether it is equal to the original string or not.

checkIfPalindrome(String s)
{

StringBuilder s2 = new StringBuilder(s);
s2.reverse();

String rev_s2 = s2.toString();

if(s.equals(rev_s2))
{ return true; }
else
{ return false; }


}

(OR)

public class Palindrome {
public static void main(String[] args) {
String str = "OOLOO";
StringBuffer newStr =new StringBuffer();
for(int i = str.length()-1; i >= 0 ; i--) {
newStr = newStr.append(str.charAt(i));
}
if(str.equalsIgnoreCase(newStr.toString())) {
System.out.println("String is palindrome");
} else {
System.out.println("String is not palindrome");
}
}

}