Package com.google.common.collect

Class ComparisonChain

  • @GwtCompatible
public abstract class ComparisonChain
extends Object
    A utility for performing a chained comparison statement. For example: 
       

   public int compareTo(Foo that) {
     return ComparisonChain.start()
         .compare(this.aString, that.aString)
         .compare(this.anInt, that.anInt)
         .compare(this.anEnum, that.anEnum, Ordering.natural().nullsLast())
         .result();
   }

    The value of this expression will have the same sign as the first nonzero comparison result in the chain, or will be zero if every comparison result was zero.

    Performance note: Even though the ComparisonChain caller always invokes its compare methods unconditionally, the ComparisonChain implementation stops calling its inputs' compareTo and compare methods as soon as one of them returns a nonzero result. This optimization is typically important only in the presence of expensive compareTo and compare implementations.

    See the Guava User Guide article on ComparisonChain.

    Since:
    2.0

    • Method Detail

      • start

        public static ComparisonChain start()
        Begins a new chained comparison statement. See example in the class documentation.

      • compare

        public abstract <T> ComparisonChain compare​(@Nullable
                                            T left,
                                            @Nullable
                                            T right,
                                            Comparator<T> comparator)
        Compares two objects using a comparator, if the result of this comparison chain has not already been determined.

      • compare

        public abstract ComparisonChain compare​(int left,
                                        int right)
        Compares two int values as specified by Ints.compare(int, int), if the result of this comparison chain has not already been determined.

      • compare

        public abstract ComparisonChain compare​(long left,
                                        long right)
        Compares two long values as specified by Longs.compare(long, long), if the result of this comparison chain has not already been determined.

      • compare

        public abstract ComparisonChain compare​(float left,
                                        float right)
        Compares two float values as specified by Float.compare(float, float), if the result of this comparison chain has not already been determined.

      • compare

        public abstract ComparisonChain compare​(double left,
                                        double right)
        Compares two double values as specified by Double.compare(double, double), if the result of this comparison chain has not already been determined.

      • compareTrueFirst

        public abstract ComparisonChain compareTrueFirst​(boolean left,
                                                 boolean right)
        Compares two boolean values, considering true to be less than false, if the result of this comparison chain has not already been determined.
        Since:
        12.0

      • compareFalseFirst

        public abstract ComparisonChain compareFalseFirst​(boolean left,
                                                  boolean right)
        Compares two boolean values, considering false to be less than true, if the result of this comparison chain has not already been determined.
        Since:
        12.0 (present as compare since 2.0)

      • result

        public abstract int result()
        Ends this comparison chain and returns its result: a value having the same sign as the first nonzero comparison result in the chain, or zero if every result was zero.