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Phantom reference are the weakest level of reference in Java; in order from strongest to weakest, they are: strong, soft, weak, phantom. An object is phantomly referenced after it has been finalized. In Java 8 and earlier versions, the reference needs to be cleared before the memory for a finalized referent can be reclaimed.
Object references in Java may be specified to be of an interface type; in each case, they must either be null, or be bound to an object that implements the interface. One benefit of using interfaces is that they simulate multiple inheritance. All classes in Java must have exactly one base class, the only exception being java.lang.Object (the ...
With Java 5.0, additional wrapper classes were introduced in the java.util.concurrent.atomic package. These classes are mutable and cannot be used as a replacement for the regular wrapper classes. Instead, they provide atomic operations for addition, increment and assignment. The atomic wrapper classes and their corresponding types are:
In the Java computer programming language, an annotation is a form of syntactic metadata that can be added to Java source code. [1] Classes, methods, variables, parameters and Java packages may be annotated. Like Javadoc tags, Java annotations can be read from source files.
For object values, the reference cannot change. This allows the Java compiler to "capture" the value of the variable at run-time and store a copy as a field in the inner class. Once the outer method has terminated and its stack frame has been removed, the original variable is gone but the inner class's private copy persists in the class's own ...
For example, if one has a List reference in Java, one cannot invoke clone() on that reference because List specifies no public clone() method. Implementations of List like Array List and Linked List all generally have clone() methods, but it is inconvenient and bad abstraction to carry around the class type of an object.
A soft reference is a reference that is garbage-collected less aggressively. The soft reference is one of the strengths or levels of 'non strong' reference defined in the Java programming language, the others being weak and phantom. In order from strongest to weakest, they are: strong, soft, weak, phantom.
clone() is a method in the Java programming language for object duplication. In Java, objects are manipulated through reference variables, and there is no operator for copying an object—the assignment operator duplicates the reference, not the object. The clone() method provides this missing functionality.