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Java in a Nutshell

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The java.lang Package

25.51 java.lang.Runtime (JDK 1.0)

This class encapsulates a number of platform-dependent system functions. The static method getRuntime() returns the Runtime object for the current platform, and this object can be used to perform system functions in a platform-independent way.

exec() starts a new process running externally to the interpreter. Note that any processes run outside of Java may be system-dependent.

exit() causes the Java interpreter to exit and return a specified return code.

freeMemory() returns the approximate amount of free memory. totalMemory() returns the total amount of memory available to the Java interpreter. gc() forces the garbage collector to run synchronously, which may free up more memory. Similarly, runFinalization() forces the finalize() methods of unreferenced objects to be run immediately. This may free up system resources that those objects were holding.

load() loads a dynamic library with a fully specified path name. loadLibrary() loads a dynamic library with only the library name specified; it looks in platform-dependent locations for the specified library. These libraries generally contain native code definitions for native methods.

traceInstructions() and traceMethodCalls() enable and disable tracing by the interpreter.

Note that some of the Runtime methods are more commonly called via the static methods of the System class.

public class Runtime extends Object {
    // No Constructor
    // Class Methods
            public static Runtime getRuntime();
        1.1public static void runFinalizersOnExit(boolean value);
    // Public Instance Methods
            public Process exec(String command) throws IOException;
            public Process exec(String command, String[] envp) throws IOException;
            public Process exec(String[] cmdarray) throws IOException;
            public Process exec(String[] cmdarray, String[] envp) throws IOException;
            public void exit(int status);
            public native long freeMemory();
            public native void gc();
        #   public InputStream getLocalizedInputStream(InputStream in);
        #   public OutputStream getLocalizedOutputStream(OutputStream out);
            public synchronized void load(String filename);
            public synchronized void loadLibrary(String libname);
            public native void runFinalization();
            public native long totalMemory();
            public native void traceInstructions(boolean on);
            public native void traceMethodCalls(boolean on);

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