You can add commands to this file or specify a different file using the -XX:CompileCommandFile option. The following commands are available:. Passes a JIT compilation option to the specified method in place of the last argument option. The compilation option is set at the end, after the method name. For example, to enable the BlockLayoutByFrequency option for the append method of the StringBuffer class, use the following:.
Instructs not to print the compile commands. By default, the commands that you specify with the -XX:CompileCommand option are printed; for example, if you exclude from compilation the indexOf method of the String class, then the following is printed to standard output:.
Sets the file from which JIT compiler commands are read. By default, the. Each line in the command file represents a command, a class name, and a method name for which the command is used. For example, this line prints assembly code for the toString method of the String class:. Adds directives from a file to the directives stack when a program starts.
See Compiler Control. Sets the list of methods separated by commas to which compilation should be restricted. Only the specified methods are compiled. Specify each method with the full class name including the packages and subpackages. For example, to compile only the length method of the String class and the size method of the List class, use the following:. Although wildcards aren't supported, you can specify only the class or package name to compile all methods in that class or package, as well as specify just the method to compile methods with this name in any class:.
Sets the number of interpreted method invocations before compilation. By default, in the server JVM, the JIT compiler performs 10, interpreted method invocations to gather information for efficient compilation.
For the client JVM, the default setting is 1, invocations. This option is ignored when tiered compilation is enabled; see the option -XX:-TieredCompilation. The following example shows how to set the number of interpreted method invocations to 5, You can completely disable interpretation of Java methods before compilation by specifying the -Xcomp option.
Sets the initial code cache size in bytes. The default value is set to KB. The initial code cache size shouldn't be less than the system's minimal memory page size. The following example shows how to set the initial code cache size to 32 KB:. Sets the maximum code size in bytes for compiled methods that should be inlined. Only compiled methods with the size smaller than the specified size is inlined. By default, the maximum code size is set to bytes:. Enables logging of compilation activity to a file named hotspot.
You can specify a different log file path and name using the -XX:LogFile option. By default, this option is disabled and compilation activity isn't logged. Sets the maximum bytecode size in bytes of a method to be inlined. By default, the maximum bytecode size is set to 35 bytes:. Sets the maximum number of nodes to be used during single method compilation. By default, the maximum number of nodes is set to 65, A nonmethod code segment containing nonmethod code, such as compiler buffers and the bytecode interpreter.
This code type stays in the code cache forever. Sets the maximum bytecode size in bytes of a trivial method to be inlined. By default, the maximum bytecode size of a trivial method is set to 6 bytes:. For bit VM on Windows, it's hsdis-amd This lets you to see the generated code, which may help you to diagnose performance issues.
By default, this option is disabled and assembly code isn't printed. Enables verbose diagnostic output from the JVM by printing a message to the console every time a method is compiled. This lets you to see which methods actually get compiled.
By default, this option is disabled and diagnostic output isn't printed. By default, this option is disabled and inlining information isn't printed. For example, to enable hardware AES, use the following flags:. These flags aren't supported on Client VM. Generates Restricted Transactional Memory RTM locking code for all inflated locks, with the normal locking mechanism as the fallback handler.
RTM is part of Intel's TSX, which is an x86 instruction set extension and facilitates the creation of multithreaded applications. If no conflict is found when running the transaction, then the memory and register modifications are committed together at the XEND instruction. A lock on a transaction is inflated when another thread tries to access the same transaction, thereby blocking the thread that didn't originally request access to the transaction. RTM requires that a fallback set of operations be specified in case a transaction aborts or fails.
RTM improves performance for highly contended locks with low conflict in a critical region which is code that must not be accessed by more than one thread concurrently. RTM also improves the performance of coarse-grain locking, which typically doesn't perform well in multithreaded applications.
Coarse-grain locking is the strategy of holding locks for long periods to minimize the overhead of taking and releasing locks, while fine-grained locking is the strategy of trying to achieve maximum parallelism by locking only when necessary and unlocking as soon as possible.
Also, for lightly contended locks that are used by different threads, RTM can reduce false cache line sharing, also known as cache line ping-pong. This occurs when multiple threads from different processors are accessing different resources, but the resources share the same cache line.
As a result, the processors repeatedly invalidate the cache lines of other processors, which forces them to read from main memory instead of their cache. This feature is applicable only when using the sun. Sun provider for SHA operations. To disable only a particular SHA intrinsic, use the appropriate corresponding option. These java options provide the ability to gather system information and perform extensive debugging.
Disables the mechanism that lets tools attach to the JVM. By default, this option is disabled, meaning that the attach mechanism is enabled and you can use diagnostics and troubleshooting tools such as jcmd , jstack , jmap , and jinfo. Sets the path and file name to where log data is written. By default, the file is created in the current working directory, and it's named hotspot.
Setting this option is equivalent to running the jmap -histo command, or the jcmd pid GC. Setting this option is equivalent to running the jstack -l command or the jcmd pid Thread. If enabled, saves jstat binary data when the Java application exits. Use the jstat command to display the performance data contained in this file as follows:.
Sets the percentage of time 0 to used to weight the current sample when computing exponential averages for the concurrent collection statistics. Sets the percentage of the old generation occupancy 0 to at which to start a CMS collection cycle. Any negative value including the default implies that the option -XX:CMSTriggerRatio is used to define the value of the initiating occupancy fraction.
Sets the number of threads used for concurrent GC. Sets the size of the regions into which the Java heap is subdivided when using the garbage-first G1 collector. The value is a power of 2 and can range from 1 MB to 32 MB. The default region size is determined ergonomically based on the heap size with a goal of approximately regions. Sets the percentage of the heap size to use as the maximum for the young generation size.
The default value is 60 percent of your Java heap. This is an experimental flag. Sets the occupancy threshold for an old region to be included in a mixed garbage collection cycle. The default occupancy is 85 percent.
Sets the percentage of the heap to use as the minimum for the young generation size. The default value is 5 percent of your Java heap. Sets the percentage of the heap 0 to 50 that's reserved as a false ceiling to reduce the possibility of promotion failure for the G1 collector. When you increase or decrease the percentage, ensure that you adjust the total Java heap by the same amount. Controls adaptive calculation of the old generation occupancy to start background work preparing for an old generation collection.
Otherwise, the old generation collection process always starts at the old generation occupancy determined by -XX:InitiatingHeapOccupancyPercent. Sets the initial size in bytes of the memory allocation pool.
This value must be either 0, or a multiple of and greater than 1 MB. The default value is selected at run time based on the system configuration. If you set this option to 0, then the initial size is set as the sum of the sizes allocated for the old generation and the young generation. The size of the heap for the young generation can be set using the -XX:NewSize option.
Sets the initial amount of memory that the JVM will use for the Java heap before applying ergonomics heuristics as a percentage of the maximum amount determined as described in the -XX:MaxRAM option. The default value is 1. The following example shows how to set the percentage of the initial amount of memory used for the Java heap:.
If adaptive sizing is disabled using the -XX:-UseAdaptiveSizePolicy option , then the -XX:SurvivorRatio option should be used to set the size of the survivor space for the entire execution of the application. The following formula can be used to calculate the initial size of survivor space S based on the size of the young generation Y , and the initial survivor space ratio R :.
The 2 in the equation denotes two survivor spaces. The larger the value specified as the initial survivor space ratio, the smaller the initial survivor space size.
By default, the initial survivor space ratio is set to 8. If the default value for the young generation space size is used 2 MB , then the initial size of the survivor space is 0. Sets the percentage of the old generation occupancy 0 to at which to start the first few concurrent marking cycles for the G1 garbage collector. A value of 0 implies nonstop concurrent GC cycles from the beginning until G1 adaptively sets this value. Sets a target for the maximum GC pause time in milliseconds.
This is a soft goal, and the JVM will make its best effort to achieve it. The specified value doesn't adapt to your heap size. By default, for G1 the maximum pause time target is milliseconds. The other generational collectors do not use a pause time goal by default. Sets the maximum size in byes of the memory allocation pool. Sets the maximum allowed percentage of free heap space 0 to after a GC event. If free heap space expands above this value, then the heap is shrunk. Try different values for these parameters until they're as low as possible yet still retain acceptable performance.
See Performance Tuning Examples for a description of using this option to keep the Java heap small by reducing the dynamic footprint for embedded applications. Sets the maximum amount of native memory that can be allocated for class metadata. By default, the size isn't limited. The amount of metadata for an application depends on the application itself, other running applications, and the amount of memory available on the system.
Sets the maximum amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics. The default value is the maximum amount of available memory to the JVM process or GB, whichever is lower. The maximum amount of available memory to the JVM process is the minimum of the machine's physical memory and any constraints set by the environment e. Specifying this option disables automatic use of compressed oops if the combined result of this and other options influencing the maximum amount of memory is larger than the range of memory addressable by compressed oops.
The following example shows how to set the maximum amount of available memory for sizing the Java heap to 2 GB:. Sets the maximum amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics as a percentage of the maximum amount determined as described in the -XX:MaxRAM option.
The default value is 25 percent. The following example shows how to set the percentage of the maximum amount of memory used for the Java heap:.
Sets the maximum amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics as a percentage of the maximum amount determined as described in the -XX:MaxRAM option for small heaps. A small heap is a heap of approximately MB. The default value is 50 percent. The following example shows how to set the percentage of the maximum amount of memory used for the Java heap for small heaps:.
Sets the maximum tenuring threshold for use in adaptive GC sizing. The largest value is The default value is 15 for the parallel throughput collector, and 6 for the CMS collector. Sets the minimum allowed percentage of free heap space 0 to after a GC event.
If free heap space falls below this value, then the heap is expanded. Try different values for these parameters until they're as low as possible, yet still retain acceptable performance.
Sets the minimum size in bytes of the memory allocation pool. The following examples show how to set the mimimum size of allocated memory to 6 MB using various units:. Sets the ratio between young and old generation sizes. By default, this option is set to 2. The following example shows how to set the young-to-old ratio to Sets the initial size in bytes of the heap for the young generation nursery.
If the size for the young generation is too low, then a large number of minor GCs are performed. If the size is too high, then only full GCs are performed, which can take a long time to complete. The following examples show how to set the initial size of the young generation to MB using various units:. Sets the number of the stop-the-world STW worker threads. Sets the amount of time in milliseconds a softly reachable object is kept active on the heap after the last time it was referenced.
The default value is one second of lifetime per free megabyte in the heap. This difference means that the Client VM tends to flush soft references rather than grow the heap, whereas the Server VM tends to grow the heap rather than flush soft references. In the latter case, the value of the -Xmx option has a significant effect on how quickly soft references are garbage collected.
This option is enabled by default. If disabled, then it immediately reduces the Java heap to the target size instead of requiring multiple garbage collection cycles. Disable this option if you want to minimize the Java heap size. You will likely encounter performance degradation when this option is disabled.
See Performance Tuning Examples for a description of using the MaxHeapFreeRatio option to keep the Java heap small by reducing the dynamic footprint for embedded applications. Identifies String objects reaching the specified age that are considered candidates for deduplication. An object's age is a measure of how many times it has survived garbage collection.
This is sometimes referred to as tenuring. Note: String objects that are promoted to an old heap region before this age has been reached are always considered candidates for deduplication. The default value for this option is 3. Sets the ratio between eden space size and survivor space size. By default, this option is set to 8. Sets the desired percentage of survivor space 0 to used after young garbage collection.
Sets the initial size in bytes of a thread-local allocation buffer TLAB. If this option is set to 0, then the JVM selects the initial size automatically. Enables the use of the parallel scavenge garbage collector also known as the throughput collector to improve the performance of your application by leveraging multiple processors.
By default, this option is disabled and the default collector is used. Enables string deduplication. By default, this option is disabled. To use this option, you must enable the garbage-first G1 garbage collector. String deduplication reduces the memory footprint of String objects on the Java heap by taking advantage of the fact that many String objects are identical.
Instead of each String object pointing to its own character array, identical String objects can point to and share the same character array. Enables the use of the Z garbage collector. This garbage collector is best for providing lowest latency with large Java heaps at some throughput cost. These java options are deprecated and might be removed in a future JDK release. They're still accepted and acted upon, but a warning is issued when they're used. Sets the file to which verbose GC events information should be redirected for logging.
The -Xloggc option overrides -verbose:gc if both are given with the same java command. Sets the initial amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics as a ratio of the maximum amount determined as described in the -XX:MaxRAM option. The default value is Sets the maximum amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics as a fraction of the maximum amount determined as described in the -XX:MaxRAM option.
The default value is 4. Sets the maximum amount of memory that the JVM may use for the Java heap before applying ergonomics heuristics as a fraction of the maximum amount determined as described in the -XX:MaxRAM option for small heaps. The default value is 2. Enables tracing of classes as they are loaded.
By default, this option is disabled and classes aren't traced. Enables tracing of all loaded classes in the order in which they're referenced. Enables tracing of constant pool resolutions. By default, this option is disabled and constant pool resolutions aren't traced. Enables tracing of the loader constraints recording. By default, this option is disabled and loader constraints recording isn't traced.
These java options are still accepted but ignored, and a warning is issued when they're used. These java options have been removed in JDK 13 and using them results in an error of:.
For the lists and descriptions of options removed in previous releases see the Removed Java Options section in:. You can shorten or simplify the java command by using argument files to specify one or more text files that contain arguments, such as options and class names, which are passed to the java command.
This let's you to create java commands of any length on any operating system. In the command line, use the at sign prefix to identify an argument file that contains java options and class names. When the java command encounters a file beginning with the at sign , it expands the contents of that file into an argument list just as they would be specified on the command line. The java launcher expands the argument file contents until it encounters the --disable- files option.
You can use the --disable- files option anywhere on the command line, including in an argument file, to stop argument files expansion. Any option that contains spaces, such as a path component, must be within quotation marks using quotation '"' characters in its entirety. File names in an argument file are relative to the current directory, not to the location of the argument file.
Use the number sign in the argument file to identify comments. All characters following the are ignored until the end of line. Additional at sign prefixes to prefixed options act as an escape, the first is removed and the rest of the arguments are presented to the launcher literally. The two lines are concatenated with the leading white spaces trimmed.
To prevent trimming the?? You can use a single argument file, such as myargumentfile in the following example, to hold all required java arguments:. You can include relative paths in argument files; however, they're relative to the current working directory and not to the paths of the argument files themselves. Any relative paths that they contain are relative to the current working directory and not to the argument files:. There are occasions when having insight into the current state of the JVM code heap would be helpful to answer questions such as:.
To provide this insight, a code heap state analytics feature has been implemented that enables on-the-fly analysis of the code heap. The analytics process is divided into two parts. You can also use an IDE like Eclipse to run the java program but we will see this part in the next tutorials.
Step 2 : Save the file as MyClass. You might be wondering why we named the file as MyClass, the point is, we always have to name the file the same as the name of the public class. If you get this error, you must first set the path before compilation. Open Command Prompt CMD , go to where you installed java on your system, and locate the bin directory. Copy the full path and write it in the command line like this. Step 4 : After compilation, the. We can now run the program. To run the program, type the below command and press Enter:.
You will be able to see the result displayed on the output. Output: sonoo jaiswal 1 3 abc. Next Topic Object vs Class. Reinforcement Learning.
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