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Java Tutorial » Development » System Class  
6.1.8.Returns the computer time in millisecondsPrevious/Next
public static long currentTimeMillis()
  1. The value represents the number of milliseconds that has elapsed since January 1, 1970 UTC.
  2. To get the string representation of the current computer time, use this:
System.out.println(new java.util.Date());

currentTimeMillis is useful if you want to time an operation.

public class MainClass {
  public static void main(String[] a) {
    long start = System.currentTimeMillis();

    // block of code to time

    long end = System.currentTimeMillis();
    System.out.println("It took " (end - start" milliseconds");
  }

}
6.1.System Class
6.1.1. java.lang.System
6.1.2. PrintStream has many print method overloads that accept different types
6.1.3. println adds a line terminator at the end of the argument
6.1.4. The err field represents a PrintStream object
6.1.5. The 'in' field represents the standard input stream
6.1.6. Array copy method
6.1.7. Terminates the running program and the current JVM
6.1.8. Returns the computer time in milliseconds
6.1.9. public static long nanoTime(): provide more precision, i.e. in nanoseconds
6.1.10. Using System.getProperty(String key) to retrieve system properties
6.1.11. Get Name of User Currently Logged In to the Computer
6.1.12. Create a user-defined property or change the value of the current property
6.1.13. Returns a default value if the specified property does not exist
6.1.14. Returns all system properties
6.1.15. Exiting a Java program
6.1.16. Terminate virtual machine using System class
6.1.17. Redirect the output of System.out to a file.
6.1.18. Calculate process elapsed time