JavaSystem Methods
System Methods
TheSystem class contains several useful methods for input, output, properties, time, and memory management.
| Method | Description | Return Type |
|---|---|---|
| currentTimeMillis() | Returns the current time in milliseconds since January 1, 1970 (Unix epoch) | long |
| nanoTime() | Returns the current value of the most precise available system timer, in nanoseconds | long |
| exit() | Terminates the running Java program. A nonzero status indicates abnormal termination | void |
| gc() | Suggests that the Java Virtual Machine run the garbage collector | void |
| getProperty() | Gets the system property indicated by the key, or returns the default value if not found | String |
| getProperties() | Returns all system properties as aProperties object | Properties |
| setProperty() | Sets the system property indicated by the key | String |
| clearProperty() | Removes the system property indicated by the key | String |
| arraycopy() | Copies elements from the source array into the destination array | void |
| identityHashCode() | Returns the default hash code of the given object (even ifhashCode() is overridden) | int |
| lineSeparator() | Returns the system-dependent line separator string (e.g.,"\n" on Linux,"\r\n" on Windows) | String |
| getenv() | Returns an unmodifiable map of the system environment variables | Map<String,String> |
| getenv() | Returns the value of the specified environment variable, ornull if it does not exist | String |
| in | Standard input stream (usually the keyboard) | InputStream |
| out | Standard output stream (usually the console). Often used withprintln() | PrintStream |
| err | Standard error output stream (usually the console) | PrintStream |
