Class Runtime

java.lang.Object
java.lang.Runtime
public class Runtime extends Object
Every Java application has a single instance of class Runtime that allows the application to interface with the environment in which the application is running. The current runtime can be obtained from the getRuntime method. An application cannot create its own instance of this class. Since: JDK1.0, CLDC 1.0 See Also:getRuntime()

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    addShutdownHook(Thread hook)
    Registers a hook that exit runs before the application closes.
    int
    availableProcessors()
    The number of processors available to the program.
    void
    exit(int status)
    Terminates the currently running Java application.
    long
    freeMemory()
    Returns the amount of free memory in the system.
    void
    gc()
    Runs the garbage collector.
    static Runtime
    getRuntime()
    Returns the runtime object associated with the current Java application.
    void
    halt(int status)
    Ends the process at once, without running the shutdown hooks.
    long
    maxMemory()
    The most memory the program may use.
    boolean
    removeShutdownHook(Thread hook)
    Unregisters a hook; whether it was registered.
    long
    totalMemory()
    Returns the total amount of memory in the Java Virtual Machine.

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • halt

      public void halt(int status)
      Ends the process at once, without running the shutdown hooks.

    • addShutdownHook

      public void addShutdownHook(Thread hook)
      Registers a hook that exit runs before the application closes.

    • removeShutdownHook

      public boolean removeShutdownHook(Thread hook)
      Unregisters a hook; whether it was registered.

    • availableProcessors

      public int availableProcessors()
      The number of processors available to the program.

    • maxMemory

      public long maxMemory()
      The most memory the program may use.

    • exit

      public void exit(int status)
      Terminates the currently running Java application. This method never returns normally. The argument serves as a status code; by convention, a nonzero status code indicates abnormal termination.

    • freeMemory

      public long freeMemory()
      Returns the amount of free memory in the system. Calling the gc method may result in increasing the value returned by freeMemory.

    • gc

      public void gc()
      Runs the garbage collector. Calling this method suggests that the Java Virtual Machine expend effort toward recycling unused objects in order to make the memory they currently occupy available for quick reuse. When control returns from the method call, the Java Virtual Machine has made its best effort to recycle all discarded objects. The name gc stands for "garbage collector". The Java Virtual Machine performs this recycling process automatically as needed even if the gc method is not invoked explicitly. The method System.gc() is the conventional and convenient means of invoking this method.

    • getRuntime

      public static Runtime getRuntime()
      Returns the runtime object associated with the current Java application. Most of the methods of class Runtime are instance methods and must be invoked with respect to the current runtime object.

    • totalMemory

      public long totalMemory()
      Returns the total amount of memory in the Java Virtual Machine. The value returned by this method may vary over time, depending on the host environment. Note that the amount of memory required to hold an object of any given type may be implementation-dependent.