Java

main difference between Java strings and C, C++ strings?

In C and C++, strings are terminated with null character. But in java, strings are not terminated with null character. Strings are treated as objects in java.

Using Iterator, we can traverse the elements only in forward direction. But, using ListIterator you can traverse the elements in both the directions.

Using Iterator, you can traverse List, Set and Queue type of objects. But using ListIterator, you can traverse only List objects.

ListIterator Methods :

boolean hasNext() –> Checks whether the list has more elements when traversing the list in forward direction.

boolean hasPrevious() –> Checks whether list has more elements when traversing the list in backward direction.

HashSet does not allow duplicate elements. If you try to insert a duplicate element, older element will be overwritten.

HashSet doesn’t maintain any order. The order of the elements will be largely unpredictable. And it also doesn’t guarantee that order will remain constant over time. If you want your elements to be ordered in some way, you can use LinkedHashSet or TreeSet.

 

The BitSet

The BitSet class implements a group of bits or flags that can be set and cleared individually.

import java.util.BitSet;

public class BitSetDemo{

public static void main(String args[]){

BitSet bits1 =new BitSet(16);

BitSet bits2 =new BitSet(16);

// set some bits

for(int i=0; i<16; i++){

if((i%2)==0) bits1.set(i);

if((i%5)!=0) bits2.set(i);

}

System.out.println("Initial pattern in bits1: ");

System.out.println(bits1);

System.out.println("\nInitial pattern in bits2: ");

System.out.println(bits2);

// AND bits

bits2.and(bits1);

System.out.println("\nbits2 AND bits1: ");

System.out.println(bits2);

volatile : volatile modifier is used in multi threaded programming. If you declare a field as volatile it will be signal to the threads that it’s value must be read from the main memory rather then their own stack. Because volatile field is common to all threads and it will be updated frequently by multiple threads.

transient : This modifier is used in serialization process. A variable which is declared as transient will not be serialized during object serialization.