13-03-25
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Q)What is the output of the following piece of code?
String s1=new String("hello");
String s2=new String("hello");
if(s1==s2)
  System.out.println("strings are equal");
else
  System.out.println("strings are not equal");

Ans:- strings are not equal

Reason:- whenever we create a String object using new keyword, 
a brand new object is created in the heap area with its own hashcode.

Q)What is the output of the following piece of code?
String s1=new String("hello");
String s2=new String("hello");
if(s1.equals(s2))
  System.out.println("strings are equal");
else
  System.out.println("strings are not equal");

Ans:- strings are equal

Q)What is the output of the following piece of code?
String s1="hello";
String s2="hello";
if(s1==s2)
  System.out.println("strings are equal");
else
  System.out.println("strings are not equal");

Ans:- strings are equal
Reason:- In string constant pool only one string object is created. Therefore
both s1&s2 reference the same object. I.e. the hashcode is the same.

Q)What is the output of the following piece of code?
String s1="hello";
String s2="hello";
if(s1.equals(s2))
   System.out.println("strings are equal");
else
   System.out.println("strings are not equal");

Ans:- strings are equal

Q)What is the difference between the following 2 statements?
            String s=null;
	    String s1="";
=>In case of  String s=null , no string object is created. Only reference
is created that holds null value(i.e. pointing to no object)

=>In case of   String s1="",    An empty string object is created.

 System.out.println(s1.length());//prints 0

Q)What is a mutable string?
=>A string is said to be mutable, if its content in its orignal location
is modifiable.

Q)How to represent a mutable string in Java?
  =>by using two Java classes mutable strings are represented.
        1)java.lang.StringBuffer
	2)java.lang.StringBuilder
  =>Whenever modification of strings is more in the application, we go for  StringBuffer
  or StringBuilder to represent strings.
Q)Java application to perform appending,insertion and delete operations on a string.
public class Test {
	public static void main(String[] args) {
		StringBuffer stringBuffer=new StringBuffer("hello");
		stringBuffer.append("! how are you");
		System.out.println(stringBuffer);
		stringBuffer.insert(0,"w");
		System.out.println(stringBuffer);
		stringBuffer.delete(0, 7);
		System.out.println(stringBuffer);		
	}
}

=>java.lang.StringBuffer is thread-safe. I.e all its methods are synchronized.

=>library methods of StringBuffer and StringBuilder are the same.But, StringBuilder
is thread-safe. I.e. its methods are non-synchronized.

Q)Java program to find if a word is a palindrome.
import java.util.Scanner;
public class Test {
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		System.out.print("Enter a word:");
		String word=scanner.next();
		StringBuffer stringBuffer=new StringBuffer(word);
		stringBuffer.reverse();
		String reversedword=new String(stringBuffer);
		if(word.equals(reversedword))
			System.out.println("It is a palindrome");
		else
			System.out.println("It is not a palindrome");
		scanner.close();
	}

}