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Java / Operators

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What is the difference between the >> and >>> operators?

>> >>>
">>" is a signed right shift. ">>>" is an unsigned right shift.
If >> is applied on a negative number, the result will still be negative. >>> ignores the sign of the number. If >>> is applied on a negative number,the result will be a positive number
The >> fills from the left with the sign bit (0 or 1). The >>> zero-fills from the left.

What is the difference between the Boolean & operator and the && operator?

&&&
& is the "bit-wise AND" operator. && is the "conditional logical AND" operator.
& always evaluates both arguments. && evaluates the first argument. if it is true, it then evaluates the second.

Explain Diamond Operator in Java.

<> denotes the diamond operator. Purpose of the diamond operator is to simplify instantiation of generic classes.

For example, see the below.

List<Integer> myList = new ArrayList<Integer>(); 
//with the diamond operator we can write as below easily.

List<Integer> myList = new ArrayList<>(); 

The Diamond Operator reduces some of Java's verbosity surrounding generics by having the compiler infer parameter types for constructors of generic classes.

Write a Java program to generate a random number between 0 to 99.

The below program uses the current time in milliseconds and apply modulo operator to pick a random number between 0 to 99.

public class RandomNumberGen {
	public static void main(String[] args) {
		long start_time = System.currentTimeMillis();

		System.out.println(start_time % 100);
	}
}
What is the difference between ++i and i++ under increment operators?

In ++i, the value of i will get incremented before it is used in the expression.

In i++, the previous value is used in the expression first, and after that i is modified and incremented.

What are Bitwise Logical Operators?

&, |, ^, and ~ are bitwise logical operators.

What is the difference between the Boolean & operator and the && operator?

For Boolean arguments, & works as the (unconditional) "logical AND" operator "&" always evaluates both arguments.

"&&" is defined for two boolean arguments. It is the "conditional logical AND" operator. "&&" ealuates the first argument. if it is true, it then evaluates the second otherwise it wonÂ’t.

Is ++i faster than i++ in for-loops in Java?

No, it is just same. in C/C++, it is considered ++i is faster as i++ involves coping it to temporarily variable. In Java, it is not the case.

Alternative to calculate modulo for power of 2 in Java.

Instead of modulo or reminder operator (%) in Java, we may use & bit wise AND operator if N is a power of 2.

For example, to calculate x % 2, since 2 is power of 1, we may use x & 1. Similarly to calculate 5%4, use 5 & 3.

The formula is x & n-1 given that n is power of 2.

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