Java utilizes an automatic garbage collector to direct memory in the object life cycle. The programmer concludes when objects are created and the Java run-time is responsible for recovering the memory once objects are no longer unavailable. One time no references to an object stay, the unreachable memory becomes appropriate to be freed automatically by the garbage collector. Something close to a memory leak may still happen if a programmer's code grips a reference to an object that is not for long time needed, characteristically when objects that are no longer required are stored in containers that are at rest occupied. If methods for a nonexistent object are known as, a "null pointer exception" is thrown.
One of the ideas at the back Java's automatic memory management model is that programmers can be spared the burden of having to carry out manual memory management. In a number of languages, memory for the creation of objects is implicitly allocated on the stack or explicitly allocated and deallocated from the heap. In the latter case the responsibility of managing memory lives with the programmer. If the program does not deallocate an object, a memory leak happens. If the program efforts to access or deallocate memory that have already been deallocated, the result is undefined and difficult to predict, and the program is on the verge of become unstable and/or crash. This can be partially cured by the use of smart pointers, but these add overhead and complexity.
Garbage collection may happen at any time. Preferably, it will occur when a program is idle. It is sure to be triggered if there is inadequate free memory on the heap to allocate a new object; this can cause a program to stall momentarily. Explicit memory management is unfeasible in Java.
Java does not hold up C/C++ style pointer arithmetic, where object addresses and unsigned integers (frequently long integers) can be used interchangeably. This permits the garbage collector to relocate referenced objects and makes sure type safety and security.
As in C++ and some additional object-oriented languages, variables of Java's primitive data types are not objects. Values of primitive types are either stored unswervingly in fields (for objects) or on the stack (for methods) rather than on the heap, as commonly true for objects (but see Escape analysis). This was an aware decision by Java's designers for presentation reasons. Due to this, Java was not considered to be an unadulterated object-oriented programming language. On the other hand, as of Java 5.0, autoboxing allows programmers to proceed as if primitive types were instances of their wrapper class.
Java holds multiple types of garbage collectors. By default, Hotspot utilizes the Concurrent Mark Sweep collector, also recognized as the CMS Garbage Collector. Though, there are also a number of other garbage collectors that can be used to deal with the Heap. For 90% of applications in Java, the CMS Garbage Collector is good enough.
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