Strings

String is one of the most fundamental classes in Java — used in virtually every program, yet deeply misunderstood by many developers.

The string pool (also called the string intern pool or string constant pool) is a special memory region maintained by the JVM that stores a single copy of each unique…

String immutability is the most important design decision in Java's String class.

Java provides two mutable string classes for scenarios where String's immutability would be inefficient: StringBuilder and StringBuffer.

The String class provides over 60 methods covering character inspection, searching, comparison, transformation, splitting, joining, formatting, and encoding.

Comparing strings in Java requires choosing the right method for the right purpose.

The == operator and the equals() method serve fundamentally different purposes in Java.

StringBuffer is a mutable sequence of characters that can be modified after creation.

StringBuilder is a mutable sequence of characters introduced in Java 5 as the preferred alternative to StringBuffer for single-threaded use.

StringTokenizer is a legacy Java class that breaks a string into tokens — substrings separated by delimiter characters.

StringJoiner is a utility class introduced in Java 8 that builds a sequence of strings separated by a delimiter, with optional prefix and suffix.

Text blocks are a Java 15 feature (previewed in Java 13 and 14) that provide multi-line string literals without manual escape sequences and concatenation.

Java was designed from the ground up for Unicode.

Regular expressions are a domain-specific language for describing patterns in text.

The Pattern class in java.util.regex is the compiled representation of a regular expression.

The Matcher class (java.util.regex.Matcher) is the engine that applies a compiled regular expression Pattern to a specific input string and performs matching operations.