Regarding intern() method of string class

[saxena neera]

Hi Folks,

I was going through string class and specially with intern method , I have developed the below code..

public class MyClass
{	
	
		 public static void main(String args[])
	 {
			 
 //How does the JVM create objects when you create a String literal?
 //To answer the first question, whenever you create a String literal, the JVM internally checks whether there is any object already 
// existing with the same value satisfying the equals() method of the string. 
 //If any such object already exists, then the reference to that existing object is returned. 
	 String s2 = "Neera is unique!";
	 System.out.println(s2.hashCode());	
			 
			 
//whenever you create an object using the new keyword, the JVM will not check for any existence of any object instead it will create a new String object 
// and return its reference. Even though there is a string existing with the same value, the JVM will return a new string because of the presence of the new keyword. 			 
	
 //The two strings' value may be equal but both the references will be pointing to two different objects.
//You can cross check this using the == operator.
	
	String s3 = new String("Neera is  unique!");
	 System.out.println(s3.hashCode());		 
	 System.out.println(s2 == s3);
	
			 
	
			 
//one of the optimization mechanisms used by the JVM the JVM will check whether the String pool maintained by the JVM contains any String objects with the same value as the str object with the equals method
//returning true. If the JVM finds such an object, then the JVM will return a reference to that object present in the String pool. If no object
 //equal to the current object is present in the String pool, then the JVM adds this string into the String pool and returns its reference to the calling object.
// The JVM adds the object to the String pool so that the next time when any string object calls the intern method, space optimization can be done
			 
						 
	 
	/* String s4 = new String(s2);//.intern();
	 System.out.println(s4.hashCode());	
	 System.out.println("-->"+"\t"+s2 == s4);*/
	
	 
	 String s4 = new String(s2).intern();
	 //System.out.println(s4.hashCode());	
	 System.out.println(s2 == s4);
	
	 		 
		 
	 }	
}

Now please advise that in above code my understandings of intern() method of string class is right or not. please advise

[Sumit Patil]

Hi,

Looking at the code i am not able to make what your understanding is about the intern() method of String class.
Please let us know the same

Thanks.

[Campbell Ritchie]

What you actually are testing is whether the new operator has a higher precedence or a lower precedence than the . member access operator.

[Athira Vineeth]

Hi,

intern() method
Returns a canonical representation for the string object.
A pool of strings, initially empty, is maintained privately by the class String.

When the intern method is invoked, if the pool already contains a string equal to this String object as determined by the equals(Object) method, then the string from the pool is returned. Otherwise, this String object is added to the pool and a reference to this String object is returned.

It follows that for any two strings s and t, s.intern() == t.intern() is true if and only if s.equals(t) is true.

For example

try this

String str="abc";
String str2=new String("abc");
System.out.println(str==str2);

this will output false

try this

String str="abc";
		String str2=new String("abc");
		System.out.println(str==str2.intern());

this will output true