String
- String literal: A string Literal in Java is basically a sequence of characters from the source character set.
- String literals initialised are an object of this String class.
💡 While printing an object, Java compiler implicitly calls toString() method.
String Memory Management
From String
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String Constant Pool
Special memory area in which string literals are stored
String Initialization using literals
Creating a String literal → JVM checks the String Constant Pool.
- Exists => Points to the same 'literal'
- Doesn't Exist => New instance created
String Initialization using new
String str = new String(); //null
String str = new String("Kya challa?")
New object created irrespective of whether the literal already exists or not
Immutability
String in Java is an Immutable Class.
From Immutable Class
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Benefits
The main benefits of immutability come in case of multi-threaded applications, functional programming and high-security systems.
- Thead safety
- Predictable behavior
- Enhanced security: ensures that sensitive data cannot be modified after its created preventing unintended or malicious change.
- Caching:
- Immutable objects can be safely shared across different parts of program.
- Hashcodes for hash-based structures can be precomputed and cached - since they won't change
- Works well with Functional Programming
- Immutability is one of the principles of functional programming
- Immutable objects ensure that functions don't modify anything outside their scope
- String Pooling: Memory management using string pool is only possible because strings are immutable.
null vs empty String
String getSome;
String getMose = "";
Both of them are not the same. "" is a literal and has a reference pointing to it in the String constant pool, while getSome has no value/reference in it so its null → default value for String.
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