12 java modifiers
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This document discusses Java modifiers including access modifiers like private, protected, and public that control class accessibility. It also covers final which makes fields unchangeable and classes uninheritable, static which associates fields and methods with a class rather than object instances, transient which excludes fields from serialization, synchronized which locks methods for thread-safe access, and volatile which prevents caching of field values between threads.
12 java modifiers
- 2. ACCESS MODIFIERS • private: only this class • protected: subclasses, classes in same package • public: every class • default: classes in same package
- 3. FINAL • on a field: can be (and needs to be) assigned only once • on a method: cannot be reimplemented • on a class: cannot have subclasses
- 4. STATIC • on a field or method: the field or method belongs to the class (not to the instance) • static block: initializes static fields class Foo { private static int baz; ! static { baz = 10; } }
- 5. TRANSIENT • on a field: will not persisted during serialization
- 6. SYNCHRONIZED • on a method: can be executed by only a thread at a time • the lock is on the instance on which the method is invoked
- 7. VOLATILE • on a field: tells the compiler that the field can be modified unexpectedly by another thread; • it is not stored in CPU caches.