important_topics.txt

***Double Precision***

If you want to have the result in a String instead of being printed to the console, use String.format() with the same arguments:

String result = String.format("%.2f", value);
Or use class DecimalFormat:

DecimalFormat df = new DecimalFormat("####0.00");
System.out.println("Value: " + df.format(value));


***BigInteger***
static BigInteger factorial(int N) 
    { 
        // Initialize result 
        BigInteger f = new BigInteger("1"); // Or BigInteger.ONE 
  
        // Multiply f with 2, 3, ...N 
        for (int i = 2; i <= N; i++) 
            f = f.multiply(BigInteger.valueOf(i)); 
  
        return f; 
    }

Comparing a doulbe with int is valid in java

**HashSet**
1. no duplicates allowed
2. does not maintain insertion order
3. null values are allowed
HashSet h = new HashSet();
h.contains(valueToBeChecked) // return true if contains else false
h.add(valueToBeAdded);	// add value
Iterator val = h.iterator();
while(val.hasNext() ) {
	sout(val.next() );	// display value
}