java.lang.System Maven / Gradle / Ivy

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Sun Microsystems Inc. owns the copyright in this file and it is provided to you for informative, as opposed to normative, use. The file and any files generated from it may be used to generate other informative documentation, such as a unified set of documents of API signatures for a platform that includes technologies expressed as Java APIs. The file may also be used to produce "compilation stubs," which allow applications to be compiled and validated for such platforms.

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This work corresponds to the API signatures of JSR 219: Foundation Profile 1.1. In the event of a discrepency between this work and the JSR 219 specification, which is available at http://www.jcp.org/en/jsr/detail?id=219, the latter takes precedence. */ package java.lang; import java.io.*; import java.util.Properties; import java.util.PropertyPermission; import java.util.StringTokenizer; import java.security.AccessController; import java.security.PrivilegedAction; import java.security.AllPermission; /** * The System class contains several useful class fields * and methods. It cannot be instantiated. *

* Among the facilities provided by the System class * are standard input, standard output, and error output streams; * access to externally defined "properties"; a means of * loading files and libraries; and a utility method for quickly * copying a portion of an array. * * @author Arthur van Hoff * @version 1.114 05/18/01 * @since JDK1.0 */ public final class System { /** * The "standard" input stream. This stream is already * open and ready to supply input data. Typically this stream * corresponds to keyboard input or another input source specified by * the host environment or user. */ public static final InputStream in = null; /** * The "standard" output stream. This stream is already * open and ready to accept output data. Typically this stream * corresponds to display output or another output destination * specified by the host environment or user. *

* For simple stand-alone Java applications, a typical way to write * a line of output data is: *

     *     System.out.println(data)
     * 

* See the println methods in class PrintStream. * * @see java.io.PrintStream#println() * @see java.io.PrintStream#println(boolean) * @see java.io.PrintStream#println(char) * @see java.io.PrintStream#println(char[]) * @see java.io.PrintStream#println(double) * @see java.io.PrintStream#println(float) * @see java.io.PrintStream#println(int) * @see java.io.PrintStream#println(long) * @see java.io.PrintStream#println(java.lang.Object) * @see java.io.PrintStream#println(java.lang.String) */ public static final PrintStream out = null; /** * The "standard" error output stream. This stream is already * open and ready to accept output data. *

* Typically this stream corresponds to display output or another * output destination specified by the host environment or user. By * convention, this output stream is used to display error messages * or other information that should come to the immediate attention * of a user even if the principal output stream, the value of the * variable out, has been redirected to a file or other * destination that is typically not continuously monitored. */ public static final PrintStream err = null; /* * This hidden constructor does not necessarily correspond to * a constructor in the original source file -- it keeps javadoc * from generating an inappropriate default constructor. */ private System() { } /** * Reassigns the "standard" input stream. * *

First, if there is a security manager, its checkPermission * method is called with a RuntimePermission("setIO") permission * to see if it's ok to reassign the "standard" input stream. *

* * @param in the new standard input stream. * * @throws SecurityException * if a security manager exists and its * checkPermission method doesn't allow * reassigning of the standard input stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since JDK1.1 */ public static void setIn(InputStream in) { } /** * Reassigns the "standard" output stream. * *

First, if there is a security manager, its checkPermission * method is called with a RuntimePermission("setIO") permission * to see if it's ok to reassign the "standard" output stream. * * @param out the new standard output stream * * @throws SecurityException * if a security manager exists and its * checkPermission method doesn't allow * reassigning of the standard output stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since JDK1.1 */ public static void setOut(PrintStream out) { } /** * Reassigns the "standard" error output stream. * *

First, if there is a security manager, its checkPermission * method is called with a RuntimePermission("setIO") permission * to see if it's ok to reassign the "standard" error output stream. * * @param err the new standard error output stream. * * @throws SecurityException * if a security manager exists and its * checkPermission method doesn't allow * reassigning of the standard error output stream. * * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission * * @since JDK1.1 */ public static void setErr(PrintStream err) { } /** * Sets the System security. * *

If there is a security manager already installed, this method first * calls the security manager's checkPermission method * with a RuntimePermission("setSecurityManager") * permission to ensure it's ok to replace the existing * security manager. * This may result in throwing a SecurityException. * *

Otherwise, the argument is established as the current * security manager. If the argument is null and no * security manager has been established, then no action is taken and * the method simply returns. * * @param s the security manager. * @exception SecurityException if the security manager has already * been set and its checkPermission method * doesn't allow it to be replaced. * @see #getSecurityManager * @see SecurityManager#checkPermission * @see java.lang.RuntimePermission */ public static void setSecurityManager(java.lang.SecurityManager s) { } /** * Gets the system security interface. * * @return if a security manager has already been established for the * current application, then that security manager is returned; * otherwise, null is returned. * @see #setSecurityManager */ public static java.lang.SecurityManager getSecurityManager() { return null; } /** * Returns the current time in milliseconds. Note that * while the unit of time of the return value is a millisecond, * the granularity of the value depends on the underlying * operating system and may be larger. For example, many * operating systems measure time in units of tens of * milliseconds. * *

See the description of the class Date for * a discussion of slight discrepancies that may arise between * "computer time" and coordinated universal time (UTC). * * @return the difference, measured in milliseconds, between * the current time and midnight, January 1, 1970 UTC. * @see java.util.Date */ public static long currentTimeMillis() { return -1; } /** * Copies an array from the specified source array, beginning at the * specified position, to the specified position of the destination array. * A subsequence of array components are copied from the source * array referenced by src to the destination array * referenced by dest. The number of components copied is * equal to the length argument. The components at * positions srcPos through * srcPos+length-1 in the source array are copied into * positions destPos through * destPos+length-1, respectively, of the destination * array. *

* If the src and dest arguments refer to the * same array object, then the copying is performed as if the * components at positions srcPos through * srcPos+length-1 were first copied to a temporary * array with length components and then the contents of * the temporary array were copied into positions * destPos through destPos+length-1 of the * destination array. *

* If dest is null, then a * NullPointerException is thrown. *

* If src is null, then a * NullPointerException is thrown and the destination * array is not modified. *

* Otherwise, if any of the following is true, an * ArrayStoreException is thrown and the destination is * not modified: *

*
• The src argument refers to an object that is not an * array. *
• The dest argument refers to an object that is not an * array. *
• The src argument and dest argument refer * to arrays whose component types are different primitive types. *
• The src argument refers to an array with a primitive * component type and the dest argument refers to an array * with a reference component type. *
• The src argument refers to an array with a reference * component type and the dest argument refers to an array * with a primitive component type. *

* Otherwise, if any of the following is true, an * IndexOutOfBoundsException is * thrown and the destination is not modified: *

*
• The srcPos argument is negative. *
• The destPos argument is negative. *
• The length argument is negative. *
• srcPos+length is greater than * src.length, the length of the source array. *
• destPos+length is greater than * dest.length, the length of the destination array. *

* Otherwise, if any actual component of the source array from * position srcPos through * srcPos+length-1 cannot be converted to the component * type of the destination array by assignment conversion, an * ArrayStoreException is thrown. In this case, let * k be the smallest nonnegative integer less than * length such that src[srcPos+k] * cannot be converted to the component type of the destination * array; when the exception is thrown, source array components from * positions srcPos through * srcPos+k-1 * will already have been copied to destination array positions * destPos through * destPos+k-1 and no other * positions of the destination array will have been modified. * (Because of the restrictions already itemized, this * paragraph effectively applies only to the situation where both * arrays have component types that are reference types.) * * @param src the source array. * @param srcPos starting position in the source array. * @param dest the destination array. * @param destPos starting position in the destination data. * @param length the number of array elements to be copied. * @exception IndexOutOfBoundsException if copying would cause * access of data outside array bounds. * @exception ArrayStoreException if an element in the src * array could not be stored into the dest array * because of a type mismatch. * @exception NullPointerException if either src or * dest is null. */ public static void arraycopy(java.lang.Object src, int srcPos, java.lang.Object dest, int destPos, int length) { } /** * Returns the same hash code for the given object as * would be returned by the default method hashCode(), * whether or not the given object's class overrides * hashCode(). * The hash code for the null reference is zero. * * @param x object for which the hashCode is to be calculated * @return the hashCode * @since JDK1.1 */ public static int identityHashCode(java.lang.Object x) { return 0; } /** * Determines the current system properties. *

* First, if there is a security manager, its * checkPropertiesAccess method is called with no * arguments. This may result in a security exception. *

* The current set of system properties for use by the * {@link #getProperty(String)} method is returned as a * Properties object. If there is no current set of * system properties, a set of system properties is first created and * initialized. This set of system properties always includes values * for the following keys: *

* Multiple paths in a system property value are separated by the path * separator character of the platform. *

* Note that even if the security manager does not permit the * getProperties operation, it may choose to permit the * {@link #getProperty(String)} operation. * * @return the system properties * @exception SecurityException if a security manager exists and its * checkPropertiesAccess method doesn't allow access * to the system properties. * @see #setProperties * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertiesAccess() * @see java.util.Properties */ public static Properties getProperties() { return null; } /** * Sets the system properties to the Properties * argument. *

* First, if there is a security manager, its * checkPropertiesAccess method is called with no * arguments. This may result in a security exception. *

* The argument becomes the current set of system properties for use * by the {@link #getProperty(String)} method. If the argument is * null, then the current set of system properties is * forgotten. * * @param props the new system properties. * @exception SecurityException if a security manager exists and its * checkPropertiesAccess method doesn't allow access * to the system properties. * @see #getProperties * @see java.util.Properties * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertiesAccess() */ public static void setProperties(Properties props) { } /** * Gets the system property indicated by the specified key. *

* First, if there is a security manager, its * checkPropertyAccess method is called with the key as * its argument. This may result in a SecurityException. *

* If there is no current set of system properties, a set of system * properties is first created and initialized in the same manner as * for the getProperties method. * * @param key the name of the system property. * @return the string value of the system property, * or null if there is no property with that key. * * @exception SecurityException if a security manager exists and its * checkPropertyAccess method doesn't allow * access to the specified system property. * @exception NullPointerException if key is * null. * @exception IllegalArgumentException if key is empty. * @see #setProperty * @see java.lang.SecurityException * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String) * @see java.lang.System#getProperties() */ public static java.lang.String getProperty(java.lang.String key) { return null; } /** * Gets the system property indicated by the specified key. *

* First, if there is a security manager, its * checkPropertyAccess method is called with the * key as its argument. *

* If there is no current set of system properties, a set of system * properties is first created and initialized in the same manner as * for the getProperties method. * * @param key the name of the system property. * @param def a default value. * @return the string value of the system property, * or the default value if there is no property with that key. * * @exception SecurityException if a security manager exists and its * checkPropertyAccess method doesn't allow * access to the specified system property. * @exception NullPointerException if key is * null. * @exception IllegalArgumentException if key is empty. * @see #setProperty * @see java.lang.SecurityManager#checkPropertyAccess(java.lang.String) * @see java.lang.System#getProperties() */ public static java.lang.String getProperty(java.lang.String key, java.lang.String def) { return null; } /** * Sets the system property indicated by the specified key. *

* First, if a security manager exists, its * SecurityManager.checkPermission method * is called with a PropertyPermission(key, "write") * permission. This may result in a SecurityException being thrown. * If no exception is thrown, the specified property is set to the given * value. *

* * @param key the name of the system property. * @param value the value of the system property. * @return the previous value of the system property, * or null if it did not have one. * * @exception SecurityException if a security manager exists and its * checkPermission method doesn't allow * setting of the specified property. * @exception NullPointerException if key is * null. * @exception IllegalArgumentException if key is empty. * @see #getProperty * @see java.lang.System#getProperty(java.lang.String) * @see java.lang.System#getProperty(java.lang.String, java.lang.String) * @see java.util.PropertyPermission * @see SecurityManager#checkPermission * @since 1.2 */ public static java.lang.String setProperty(java.lang.String key, java.lang.String value) { return null; } /** * Terminates the currently running Java Virtual Machine. The * argument serves as a status code; by convention, a nonzero status * code indicates abnormal termination. *

* This method calls the exit method in class * Runtime. This method never returns normally. *

* The call System.exit(n) is effectively equivalent to * the call: *

     * Runtime.getRuntime().exit(n)
     * 

* If process model exists, System.exit() must rely on the process * exiting to release resources. *

* If process model does not exist, and a security manager exists, * the security manager by default must prohibit calls to System.exit() * by throwing SecurityException. Otherwise, the system will hang * indefinitely when called, *

* @param status exit status. * @throws SecurityException * if a security manager exists and its checkExit * method doesn't allow exit with the specified status. * @see java.lang.Runtime#exit(int) */ public static void exit(int status) { } /** * Runs the garbage collector. *

* Calling the gc 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 a best effort to reclaim space from all discarded * objects. *

* The call System.gc() is effectively equivalent to the * call: *

     * Runtime.getRuntime().gc()
     * 

* Calling this method suggests that the Java Virtual Machine expend * effort toward running the finalize methods of objects * that have been found to be discarded but whose finalize * methods have not yet been run. When control returns from the * method call, the Java Virtual Machine has made a best effort to * complete all outstanding finalizations. *

* The call System.runFinalization() is effectively * equivalent to the call: *

     * Runtime.getRuntime().runFinalization()
     * 

* The call System.load(name) is effectively equivalent * to the call: *

     * Runtime.getRuntime().load(name)
     * 

* The call System.loadLibrary(name) is effectively * equivalent to the call *

     * Runtime.getRuntime().loadLibrary(name)
     *