What is a string in Java?

A string in Java is a sequence of characters. It is represented by the String class.

Key features:

• Immutability: After creating a String object, its contents cannot be changed. Any operation that appears to modify the string (e.g., concatenation) actually creates a new String object.
• String Pool: Java uses the String Pool for efficient management of string literals. When a string literal (e.g., "hello") is created, the JVM first searches for it in the pool. If it exists, a reference to the existing object is returned. If not, a new object is created in the pool, and a reference to it is returned.
• Creation:
  • Using a string literal: String s1 = "hello"; (uses the String Pool).
  • Using the new operator: String s2 = new String("world"); (creates a new object on the heap, even if "world" already exists in the pool).
• Comparison: To compare the contents of strings, use the equals() method, not the == operator. The == operator compares object references.

Example:

// Creating a string using a literal (from the pool)
String s1 = "Java";

// Creating a string using new (a new object on the heap)
String s2 = new String("Java");

// Comparing contents (correct)
boolean contentEquals = s1.equals(s2); // true

// Comparing references (not correct for content comparison)
boolean referenceEquals = (s1 == s2); // false

System.out.println("Contents are the same: " + contentEquals);
System.out.println("References are the same: " + referenceEquals);