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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.
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.
Autoboxing is the term for getting a reference type out of a value type just through type conversion (either implicit or explicit). The compiler automatically supplies the extra source code that creates the object. For example, in versions of Java prior to J2SE 5.0, the following code did not compile:
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 ...
A method has a return value, a name and usually some parameters initialized when it is called with some arguments. Similar to C++, methods returning nothing have return type declared as void. Unlike in C++, methods in Java are not allowed to have default argument values and methods are usually overloaded instead.
The Stack offers methods to put a new object on the Stack (method push(E e)) and to get objects from the Stack (method pop()). A Stack returns the object according to last-in-first-out (LIFO), e.g. the object which was placed latest on the Stack is returned first. java.util.Stack is a standard implementation of a stack provided by Java.
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.
An object will provide a particular interface if its class contains code that implement the method of that interface. An interface also defines types that can be used to declare the type of variables or parameters and return values of methods. Actions An action in object-oriented programming (OOP) is initiated by an object invoking a method in ...