Stopwatch (Guava: Google Core Libraries for Java 15.0 API)

java.lang.Object
- com.google.common.base.Stopwatch

```
@Beta
@GwtCompatible(emulated=true)
public final class Stopwatch
extends Object
```
An object that measures elapsed time in nanoseconds. It is useful to measure elapsed time using this class instead of direct calls to System.nanoTime() for a few reasons:
- An alternate time source can be substituted, for testing or performance reasons.
- As documented by nanoTime, the value returned has no absolute meaning, and can only be interpreted as relative to another timestamp returned by nanoTime at a different time. Stopwatch is a more effective abstraction because it exposes only these relative values, not the absolute ones.
Basic usage:
```
   Stopwatch stopwatch = Stopwatch.createStarted();
   doSomething();
   stopwatch.stop(); // optional

   long millis = stopwatch.elapsed(MILLISECONDS);

   log.info("time: " + stopwatch); // formatted string like "12.3 ms"
```
Stopwatch methods are not idempotent; it is an error to start or stop a stopwatch that is already in the desired state.
When testing code that uses this class, use createUnstarted(Ticker) or createStarted(Ticker) to supply a fake or mock ticker. This allows you to simulate any valid behavior of the stopwatch.
Note: This class is not thread-safe.
Since:

10.0

Author:

Kevin Bourrillion

Constructor Summary

Constructors
Constructor and Description
`Stopwatch()` Deprecated. Use `createUnstarted()` instead. This constructor is scheduled to be removed in Guava release 17.0.
`Stopwatch(Ticker ticker)` Deprecated. Use `createUnstarted(Ticker)` instead. This constructor is scheduled to be removed in Guava release 17.0.

Method Summary

Methods
Modifier and Type	Method and Description
`static Stopwatch`	`createStarted()` Creates (and starts) a new stopwatch using `System.nanoTime()` as its time source.
`static Stopwatch`	`createStarted(Ticker ticker)` Creates (and starts) a new stopwatch, using the specified time source.
`static Stopwatch`	`createUnstarted()` Creates (but does not start) a new stopwatch using `System.nanoTime()` as its time source.
`static Stopwatch`	`createUnstarted(Ticker ticker)` Creates (but does not start) a new stopwatch, using the specified time source.
`long`	`elapsed(TimeUnit desiredUnit)` Returns the current elapsed time shown on this stopwatch, expressed in the desired time unit, with any fraction rounded down.
`long`	`elapsedMillis()` Deprecated. Use `stopwatch.elapsed(MILLISECONDS)` instead. This method is scheduled to be removed in Guava release 16.0.
`long`	`elapsedTime(TimeUnit desiredUnit)` Deprecated. Use `elapsed(TimeUnit)` instead. This method is scheduled to be removed in Guava release 16.0.
`boolean`	`isRunning()` Returns `true` if `start()` has been called on this stopwatch, and `stop()` has not been called since the last call to `start()`.
`Stopwatch`	`reset()` Sets the elapsed time for this stopwatch to zero, and places it in a stopped state.
`Stopwatch`	`start()` Starts the stopwatch.
`Stopwatch`	`stop()` Stops the stopwatch.
`String`	`toString()` Returns a string representation of the current elapsed time.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - Stopwatch
```
@Deprecated
public Stopwatch()
```
    Deprecated. Use createUnstarted() instead. This constructor is scheduled to be removed in Guava release 17.0.
    
    Creates (but does not start) a new stopwatch using System.nanoTime() as its time source.
  - Stopwatch
```
@Deprecated
public Stopwatch(Ticker ticker)
```
    Deprecated. Use createUnstarted(Ticker) instead. This constructor is scheduled to be removed in Guava release 17.0.
    
    Creates (but does not start) a new stopwatch, using the specified time source.
- Method Detail
  - createUnstarted
```
public static Stopwatch createUnstarted()
```
    Creates (but does not start) a new stopwatch using System.nanoTime() as its time source.
    
    Since:
    
    15.0
  - createUnstarted
```
public static Stopwatch createUnstarted(Ticker ticker)
```
    Creates (but does not start) a new stopwatch, using the specified time source.
    
    Since:
    
    15.0
  - createStarted
```
public static Stopwatch createStarted()
```
    Creates (and starts) a new stopwatch using System.nanoTime() as its time source.
    
    Since:
    
    15.0
  - createStarted
```
public static Stopwatch createStarted(Ticker ticker)
```
    Creates (and starts) a new stopwatch, using the specified time source.
    
    Since:
    
    15.0
  - isRunning
```
public boolean isRunning()
```
    Returns true if start() has been called on this stopwatch, and stop() has not been called since the last call to start().
  - start
```
public Stopwatch start()
```
    Starts the stopwatch.
    
    Returns:
    this Stopwatch instance
    
    Throws:
    
    IllegalStateException - if the stopwatch is already running.
  - stop
```
public Stopwatch stop()
```
    Stops the stopwatch. Future reads will return the fixed duration that had elapsed up to this point.
    
    Returns:
    this Stopwatch instance
    
    Throws:
    
    IllegalStateException - if the stopwatch is already stopped.
  - reset
```
public Stopwatch reset()
```
    Sets the elapsed time for this stopwatch to zero, and places it in a stopped state.
    
    Returns:
    this Stopwatch instance
  - elapsed
```
public long elapsed(TimeUnit desiredUnit)
```
    Returns the current elapsed time shown on this stopwatch, expressed in the desired time unit, with any fraction rounded down.
    Note that the overhead of measurement can be more than a microsecond, so it is generally not useful to specify TimeUnit.NANOSECONDS precision here.
    
    Since:
    
    14.0 (since 10.0 as elapsedTime())
  - elapsedTime
```
@Deprecated
public long elapsedTime(TimeUnit desiredUnit)
```
    Deprecated. Use elapsed(TimeUnit) instead. This method is scheduled to be removed in Guava release 16.0.
    
    Returns the current elapsed time shown on this stopwatch, expressed in the desired time unit, with any fraction rounded down.
    Note that the overhead of measurement can be more than a microsecond, so it is generally not useful to specify TimeUnit.NANOSECONDS precision here.
  - elapsedMillis
```
@Deprecated
public long elapsedMillis()
```
    Deprecated. Use stopwatch.elapsed(MILLISECONDS) instead. This method is scheduled to be removed in Guava release 16.0.
    
    Returns the current elapsed time shown on this stopwatch, expressed in milliseconds, with any fraction rounded down. This is identical to elapsed(TimeUnit.MILLISECONDS).
  - toString
```
@GwtIncompatible(value="String.format()")
public String toString()
```
    Returns a string representation of the current elapsed time.
    
    Overrides:
    
    toString in class Object
    
    Returns:
    a string representation of the object.

Class Stopwatch

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Stopwatch

Stopwatch

Method Detail

createUnstarted

createUnstarted

createStarted

createStarted

isRunning

start

stop

reset

elapsed

elapsedTime

elapsedMillis

toString