JAVA : System.currentTimeMillis()

System.currentTimeMillis()

• returns current value of running java virtual machine high resolution time source in nanoseconds.
• The value returned represents nanoseconds since some fixed but arbitrary origin time,
• other jvm instance will use different origin. Origin is nothing but used to keep track of the time from the start of the jvm

• long startTime=System.currentTimeMillis();
  //output : 1663132233612
  

How to use this

 long startTime = System.nanoTime(); 
   // ... the code being measured ...   
 long estimatedTime = System.nanoTime() - startTime;