String Literal Vs String Object in Java

The Java.lang.String or String class, which is a notable class in API. With its several unique features that are not immediately apparent to many programmers, the String class is unique in the Java API. Understanding the String class is a prerequisite for learning Java. It is in addition to the standard queries about why String is final or equals vs. == operator. Therefore, this it also includes the String Literal and String Object in API's.

String Literal:

In Java, a string literal is essentially a string of characters from the source character set that the developers use to fill in string objects or show text to the user. These characters, which are denoted by two quotation marks, may consist of any combination of letters, numbers, or symbols.

Declaration Syntax:

In simple terms, we are invoking the intern() method on String when you declare a string in this manner. The technique makes use of an internal string object pool. No new String object will be generated if a string value, such as "abc," already exists. In that case, str will reference the existing string.

String Object:

A string object allows you to operate with a string of characters. It essentially encapsulates all of JavaScript's primitive string data types and includes several convenience methods. JavaScript's primary role is to translate strings into string objects from string primitives automatically.

Declaration Syntax:

An object made of strings is the one that follows. Even if "abc" is already in the reference pool, the JVM is compelled to establish a new string reference using this technique. Consequently, since a string object creates a new string each time it is processed when performance is compared between the string literal and string object, the string object will always execute more slowly than the string literal.

For example, what differentiates the String objects formed in the following two expressions:

String strObj = new String("abc"); and
String strLit = "abc";

There is a slight distinction between the two expressions, but they both return a String object. Whenever we use the new() operator to construct a String object, heap memory is always used to generate the new object. However, when we construct an object using the String literal syntax, such as "abc," it can return an existing object from the String pool, which is a cache of String objects in Perm gen space that was recently migrated to heap space in the Java version. If not, it will generate a fresh string object and store it in a string pool for later usage.

Example:

The performance(time) parameter is taken for utilizing string literals versus string objects is compared in this Java program. Two strings, "Hello" and "World," are initialized inside of loops; one uses string literals, and the other uses string objects. By keeping track of the beginning and ending times of every loop and computing the difference, the program determines how long each initialization procedure takes.

Ultimately, the total time spent on each technique is printed down. It helps us to demonstrate how utilizing string literals-which are kept in the string pool and reused if they already exist-and directly generating new string objects differ in terms of execution time.

Implementation:

FileName: DiffPerformanceStringLiteralObject.java

import java.io.*;
import java.util.*;
public class DiffPerformanceStringLiteralObject
{ 
	public static void main(String args[]) 
	{	 
		// Initialization time for the String Literal
		long start_time1 = System.currentTimeMillis(); 
		for (int i = 0; i < 10000; i++) 
		{ 
			String str1 = "Hello"; 
			String str2 = "World"; 
		} 
		long end_time1 = System.currentTimeMillis(); 
		long total_time1 = end_time1 - start_time1; 
		System.out.println("The total time taken to execute for"+ " string literal = " + total_time1); 
		// Initialization time for the String Object 
		long start_time2 = System.currentTimeMillis(); 
		for (int i = 0; i < 10000; i++) 
		{ 
			String str3 = new String("Hello"); 
			String str4 = new String("World"); 
		} 
		long end_time2 = System.currentTimeMillis(); 
		long total_time2 = end_time2 - start_time2; 
		System.out.println("The total time taken to execute for"+ " string object = " + total_time2); 
	} 
}

Output

The total time taken to execute for string literal = 0
The total time taken to execute for string object = 1

Complexity Analysis:

The above code's time complexity is O(N), where N represents the number of iterations, and the space complexity is O(1).

Differences between String Literal and String Object:

STRING LITERAL	STRING OBJECT
Double quotes ("") are used to enclose the string when creating string literals.	The String constructor and the new keyword are used to generate String objects.
Java looks for an identical string in the string pool, a designated location in the heap memory, when you generate a string literal.	Java allocates RAM on the heap to hold the string when you create a string object with a new String().
Java reuses the string and only returns a reference to it if the same string already exists in the string pool.	Using a new String() will generate a new object on the heap regardless of the string pool, even if the same string already exists there.
Java generates a new string object in the pool and returns its reference if the string does not already exist there.	Instead of being stored in the string pool, string objects can be stored in the general heap memory.
The string pool, shared by several computer components and located on the heap memory, is where string literals are maintained.	New String() creates string objects that are allocated memory in the general heap, with each object having its own memory space.
Since string literals created with the same content will have the same memory reference, a == comparison will treat them equally.	As distinct memory references will be used to build string objects with the same content using new String(), they cannot be compared using the == operator unless they are specifically compared using the .equals() function.
Due to string interning, which is the reuse of already-existing strings in the string pool, string literals are typically more performant and memory-efficient.	Even when a string is identical and already exists in the string pool, string objects made with new String() are less efficient because they constantly allocate fresh memory space on the heap.
Example: String str = "abc";	Example: String str = new String("abc");