Module org.hsqldb
Package org.hsqldb.lib

Class CountUpDownLatch

  • public class CountUpDownLatch
extends java.lang.Object
    A variation on CountDownLatch to allow counting up as well as down.
    Author:
    Campbell Burnet (campbell-burnet@users dot sourceforge.net)

    • Constructor Summary

      Constructors 
      Constructor Description
      CountUpDownLatch()
      Default constructor.
      CountUpDownLatch​(int initialCount)
      Constructs a new CountUpDownLatch initialized with the given initialCount.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void await()
      Causes the current thread to wait until count reaches zero, unless the thread is interrupted.
      boolean await​(long timeout, java.util.concurrent.TimeUnit unit)
      Causes the current thread to wait until count reaches zero, unless the thread is interrupted, or the specified waiting time elapses.
      boolean countDown()
      Decrements the count of the latch, releasing all waiting threads if the count transitions to zero.
      boolean countDown​(int amount)
      Decrements the count of the latch by the given amount, releasing all waiting threads if count transitions to zero.
      boolean countUp()
      Increments the count of the latch.
      boolean countUp​(int amount)
      Increments the count of the latch by the given amount.
      boolean equals​(java.lang.Object obj)
      Returns true if and only if this and obj refer to the same object (this == obj has the value true).
      boolean equals​(CountUpDownLatch other)
      Returns true if and only if this and obj refer to the same object (this == obj has the value true).
      int getCount()
      Returns the current count.
      int hashCode()
      As much as is reasonably practical, returns distinct integers for distinct objects.
      boolean setCount​(int newCount)
      Updates count to the requested newCount, returning true on transition to zero.
      java.lang.String toString()
      Returns a string representation of this object.

      • Methods inherited from class java.lang.Object

        getClass, notify, notifyAll, wait, wait, wait

    • Constructor Detail

      • CountUpDownLatch

        public CountUpDownLatch()
        Default constructor.

        Equivalent to new CountUpDownLatch(0)

      • CountUpDownLatch

        public CountUpDownLatch​(int initialCount)
        Constructs a new CountUpDownLatch initialized with the given initialCount.
        Parameters:
        initialCount - the initial count
        Throws:
        java.lang.IllegalArgumentException - if initialCount is negative

    • Method Detail

      • await

        public void await()
           throws java.lang.InterruptedException
        Causes the current thread to wait until count reaches zero, unless the thread is interrupted.

        If the current count is already zero, then this method returns immediately.

        If the current count is greater than zero, then the current thread becomes disabled for thread scheduling purposes and lies dormant until either:

        If the current thread:
        • has its interrupted status set on entry to this method; or
        • is interrupted while waiting,
        then InterruptedException is thrown and the current thread's interrupted status is cleared.
        Throws:
        java.lang.InterruptedException - if the current thread is interrupted while waiting

      • await

        public boolean await​(long timeout,
                     java.util.concurrent.TimeUnit unit)
              throws java.lang.InterruptedException
        Causes the current thread to wait until count reaches zero, unless the thread is interrupted, or the specified waiting time elapses.

        If the current count is zero, then this method returns immediately with the value true.

        If the current count is greater than zero, then the current thread becomes disabled for thread scheduling purposes and lies dormant until either:

        • The count reaches zero due to an invocation of countDown(), countDown(int}, or setCount(int) setCount(int)}
        • Some other thread interrupts the current thread
        • The specified waiting time elapses.
        If the count reaches zero then the method returns with the value true.

        If the current thread:

        • has its interrupted status set on entry to this method; or
        • is interrupted while waiting,
        then InterruptedException is thrown and the current thread's interrupted status is cleared.

        If the specified waiting time elapses then the value false is returned. If the time is less than or equal to zero, the method will not wait at all.

        Parameters:
        timeout - the maximum time to wait
        unit - the time unit of the timeout argument
        Returns:
        true if the count reached zero and false if the waiting time elapsed before the count reached zero
        Throws:
        java.lang.InterruptedException - if the current thread is interrupted while waiting

      • countUp

        public boolean countUp()
        Increments the count of the latch.

        Returns:
        true if count transitioned from zero to a new value
        Throws:
        java.lang.ArithmeticException - when the operation would otherwise cause a silent numeric overflow, resulting in a negative count.

      • countUp

        public boolean countUp​(int amount)
        Increments the count of the latch by the given amount.

        Parameters:
        amount - by which to increment count
        Returns:
        true if count transitioned from zero to a new value
        Throws:
        java.lang.ArithmeticException - when the operation would otherwise cause a silent numeric overflow, resulting in a negative count.
        java.lang.IllegalArgumentException - if amount is less than one.

      • countDown

        public boolean countDown()
        Decrements the count of the latch, releasing all waiting threads if the count transitions to zero.

        If the current count is zero, no action occurs and false is returned immediately;

        Returns:
        true if count transitions to zero

      • countDown

        public boolean countDown​(int amount)
        Decrements the count of the latch by the given amount, releasing all waiting threads if count transitions to zero.

        If the current count is zero, no action occurs and false is returned immediately; otherwise, count is decremented by the lesser of amount and current count i.e. if amount is greater than current count, then new count is zero, else new count is current count minus amount.

        Parameters:
        amount - by which to decrement the count
        Returns:
        true if count transitions to zero
        Throws:
        java.lang.IllegalArgumentException - when amount is non-positive

      • getCount

        public int getCount()
        Returns the current count.

        Because another thread may update count at any time, typically this should not be used to compute input values for any of the @{code count} mutating methods and instead should be reserved for debugging and testing purposes (e.g. to assert that the current count is the expected count, given a set of know operations has occurred and given that it is known no other threads could be updating the count)

        Returns:
        the current count

      • setCount

        public boolean setCount​(int newCount)
        Updates count to the requested newCount, returning true on transition to zero.

        If newCount is zero and the current count is zero, no action occurs and false is returned immediately. immediately;

        Parameters:
        newCount - to which to update count; must be non-negative.
        Returns:
        true if count transitions to zero.
        Throws:
        java.lang.IllegalArgumentException - when newCount is negative

      • toString

        public java.lang.String toString()
        Returns a string representation of this object.

        Overrides:
        toString in class java.lang.Object
        Returns:
        a string identifying this latch, as well as its current count.

      • hashCode

        public int hashCode()
        As much as is reasonably practical, returns distinct integers for distinct objects.
        Overrides:
        hashCode in class java.lang.Object
        Returns:
        a hash code value for this latch. This method is supported for the benefit of hash tables

      • equals

        public boolean equals​(CountUpDownLatch other)
        Returns true if and only if this and obj refer to the same object (this == obj has the value true).
        Parameters:
        other - to test.
        Returns:
        if and only if this == obj

      • equals

        public boolean equals​(java.lang.Object obj)
        Returns true if and only if this and obj refer to the same object (this == obj has the value true).
        Overrides:
        equals in class java.lang.Object
        Parameters:
        obj - to test.
        Returns:
        if and only if this == obj