Java String: Creation, Concatenation, Comparison, and Common Problem Solutions

In Java, String is an immutable text class used to store text data. It can be created in two ways: direct assignment (reusing the constant pool, where identical content references the same object) and the new keyword (creating a new object in the heap with a different reference). For concatenation operations, the '+' sign is intuitive but inefficient for loop-based concatenation. The concat() method returns a new string without modifying the original. For massive concatenation, StringBuilder (single-threaded) or StringBuffer (multi-threaded) is more efficient. When comparing strings, '==' checks for reference equality, while equals() compares content. For empty strings, use isEmpty() or length() == 0, and always check for null first. Common mistakes include confusing '==' with equals(), and inefficient loop-based concatenation using '+'. These should be avoided by using equals() and StringBuilder. Mastering these concepts helps prevent errors and improve code efficiency.