The article explains Java's primitive types versus object types, introduces wrapper classes such as Integer, Double and Boolean, demonstrates manual and automatic boxing/unboxing, reveals the -128~127 Integer cache trap, shows common wrapper APIs, and warns about null‑unboxing NPEs.
This article explains how == compares primitive values and object references, why Object.equals() defaults to ==, how classes like String and Integer override equals(), the impact of the string constant pool, integer caching, auto‑boxing, floating‑point pitfalls, and best practices for correctly comparing objects in Java.
The article explains why comparing two Integer objects with `==` returns true for values within -128 to 127 but false for larger numbers, detailing Java’s integer cache, reference vs. value equality, and the correct use of `.equals()` to avoid subtle bugs.
This article explores why using an Integer as a lock can cause synchronized to malfunction, demonstrates the issue with a ticket‑selling example, analyzes thread dumps and JVM bytecode, and presents reliable alternatives such as class‑level locks or map‑based lock objects.
This article explains why Java’s Integer autoboxing caches values between -128 and 127, causing the == operator to report true for those numbers, and shows how to avoid the pitfall by using equals() instead.
This article explains why the == operator returns true for small Integer values in Java, detailing the internal IntegerCache mechanism, demonstrating the behavior with code examples, and showing how reflection can manipulate the cache, highlighting both the benefits and potential pitfalls of this optimization.
