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In some programming language environments (at least one proprietary Lisp implementation, for example), [citation needed] the value used as the null pointer (called nil in Lisp) may actually be a pointer to a block of internal data useful to the implementation (but not explicitly reachable from user programs), thus allowing the same register to be used as a useful constant and a quick way of ...
In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
A snippet of Java code with keywords highlighted in bold blue font. The syntax of Java is the set of rules defining how a Java program is written and interpreted.. The syntax is mostly derived from C and C++.
The language does not provide any explicit pointer manipulation operators. It is still possible for code to attempt to dereference a null reference (null pointer), however, which results in a run-time exception being thrown. The space occupied by unreferenced memory objects is recovered automatically by garbage collection at run-time. [20]
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. It is a general-purpose programming language intended to let programmers write once, run anywhere (), [16] meaning that compiled Java code can run on all platforms that support Java without the need to recompile. [17]
Catch ex As ExceptionType ' Handle Exception of a specified type (i.e. DivideByZeroException, OverflowException, etc.) Catch ex As Exception ' Handle Exception (catch all exceptions of a type not previously specified) Catch ' Handles anything that might be thrown, including non-CLR exceptions.
Dereferencing a null pointer and then assigning to it (writing a value to a non-existent target) also usually causes a segmentation fault: int * ptr = NULL ; * ptr = 1 ; The following code includes a null pointer dereference, but when compiled will often not result in a segmentation fault, as the value is unused and thus the dereference will ...
Java does not have uninitialized variables. Fields of classes and objects that do not have an explicit initializer and elements of arrays are automatically initialized with the default value for their type (false for boolean, 0 for all numerical types, null for all reference types). [ 4 ]