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The little ape had been in C + + for two years and was transferred to the Java Project last month, so the first essay thought of 818 Java memory optimization.The first optimization of this kind of thing, definitely should be put to the last to do, but in the process of writing code to develop good habits is also very important. Here we recommend a book, "Writing
exhausted.Garbage collectionGarbage collection (garbage collection, referred to as GC) automatically empties objects that are no longer used in the heap. The garbage collection mechanism, which first appeared in 1959, was used to solve problems in the Lisp language. Garbage collection is a major feature of Java. Not all languages have garbage collection capabilities. For example, there is no mechanism for garbage collection in C + +. The programmer n
other additional information is generally classified as a class, called the stack frame information.Third, the local method stackThe local method stack (Native methods stack) is very similar to the virtual machine stack, but the difference between them is that the virtual machine stack executes Java methods (that is, bytecode) services for the virtual machine, while the local method stack is the Native method service used by the virtual machine. As w
The JVM can use 2 different kinds of memory: heap memory and out -of-heap memory.Heap memory is fully allocated and freed by the JVM, and if the program does not have a defective code that causes memory leaks, you will not encounter the Java.lang.OutOfMemoryError error.The use of out-of-heap
of Java programming. Obtain products and technologies Jtune: a free jtune tool that allows you to use GC logs and graphically display the heap size, GC duration, and other useful memory management data. Discussion Join this forum. (You can also click the forum link at the top or bottom of the article to participate in the discussion .
memory overflows in the permanent zoneSome other memory overflow scenarios are listed below"Situation One":Java.lang.OutOfMemoryError:Java Heap Space: This is the Java heap memory is not enough, one reason is really not enough, another reason is that the program has a dead loop;If the
+ +. The programmer needs to manually free the memory in the heap.Because there is no need to manually free up memory, programmers can reduce the chance of making mistakes in programming. With garbage collection, programmers can avoid some pointers and memory leaks related
store static type data, such as Java Class, Method, and so on. Persistent generations have no significant impact on garbage collection. However, some applications may dynamically generate or invoke some classes, such as Hibernate CGLib, where it is often necessary to set a large, persistent generation space to store dynamically increasing types during these runs.So, when a group of objects are generated, the memo
Java memory can be divided into: heap and meta space. To View the heap: Jmap-heap PID View Metaspace: Use JSTAT-GC pid mc Mu. to view other uses in the process: The RS occupancy in top is minus the footprint in the jmap-heap. /proc/$PID/maps Smaps is a more detailed information Pamp Pid:anon means memory allocation. $cat/proc/1756/maps | grep deleted to search fo
In some large-scale applications, memory settings of Java Virtual Machine (JVM) are particularly important. To achieve good efficiency in the project, GC (garbage collection) settings are the first step. Permgen Space: The full name is permanent generation space. That is to say, it is a permanent storage area, used to store class and meta information. When the class is loaded, it is placed in this area he
static to identify a particular element of an object that is static, but the Java object itself never resides in a static storage space. 5. Constant storage (constant storage). Constant values are usually stored directly inside the program code, and it is safe to do so because they are never changed. Sometimes, in an embedded system, the constants themselves are separated from the rest, so in this case, you can choose to place them in ROM6. Non-RAM s
Heap and non-heap memoryAccording to the official statement: "A Java virtual machine has a heap. The heap is the runtime data area, and the memory of all class instances and arrays is allocated from this place. The heap is created when the Java Virtual Machine is started ." "Memory outside of the heap in JVM is called
Java memory Mechanism:Java divides memory into two types: one is stack memory and the other is heap memory.Some basic types of variables and object reference variables defined in the function are allocated in the stack memory of the function, and when a variable is defined i
in the static store that persists while the program is running. You can use the keyword static to identify a particular element of an object that is static, but the Java object itself never resides in a static storage space. 5. constant Storage (constantstorage). Constant values are usually stored directly inside the program code, and it is safe to do so because they are never changed. Sometimes, in an embedded system, the constants themselves are se
1. Why memory leaks occurHow does Java detect internal leaks? We need some tools to detect and find memory leaks, otherwise it's easy to have a down-machine problem.The most convenient place to write Java programs is that we do not need to manage the allocation and release of memor
A lot of information on the web when describing the Java memory model, will introduce a main memory, and then each worker thread has its own working memory. The data is in main memory and there is a copy in the working RAM. There is a variety of atomic operations between wor
exhausted.Garbage collectionGarbage collection (garbage collection, referred to as GC) automatically empties objects that are no longer used in the heap. The garbage collection mechanism, which first appeared in 1959, was used to solve problems in the Lisp language. Garbage collection is a major feature of Java. Not all languages have garbage collection capabilities. For example, there is no mechanism for garbage collection in C + +. The programmer n
whether the class represented by the symbol is loaded parsing initializationIf not, the load class3. After the class is loaded, allocate memory for the new object (the allocated memory size is determined after the class is loaded)Memory allocation Method:If the memory is a regular pointer collision (where the pointer
Does Java produce memory leaks? First of all, the answer is yes. Java has a garbage collector, but leaks still exist.Java memory leaks are not the same as the C + + memory leak concept: the memory leak in C + + means that malloc h
Write NIO programs often use Bytebuffer to read or write data, then use bytebuffer.allocate (capability) or bytebuffer.alloctedirect (capability) To allocate the cache? The first is to allocate JVM heap memory, which belongs to the GC jurisdiction, which is relatively slow due to the need for copying, and the second is to allocate OS local memory, which is not in GC jurisdiction, and is relatively fast beca
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