Java example source code file (Cut.java)

This example Java source code file (Cut.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

aboveall, abovevalue, annotation, assertionerror, belowall, boundtype, comparable, cut, discretedomain, illegalstateexception, instance, open, override, string, util

The Cut.java Java example source code

/*
 * Copyright (C) 2009 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.primitives.Booleans;

import java.io.Serializable;
import java.util.NoSuchElementException;

import javax.annotation.Nullable;

/**
 * Implementation detail for the internal structure of {@link Range} instances. Represents
 * a unique way of "cutting" a "number line" (actually of instances of type {@code C}, not
 * necessarily "numbers") into two sections; this can be done below a certain value, above
 * a certain value, below all values or above all values. With this object defined in this
 * way, an interval can always be represented by a pair of {@code Cut} instances.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
abstract class Cut<C extends Comparable> implements Comparable>, Serializable {
  final C endpoint;

  Cut(@Nullable C endpoint) {
    this.endpoint = endpoint;
  }

  abstract boolean isLessThan(C value);

  abstract BoundType typeAsLowerBound();

  abstract BoundType typeAsUpperBound();

  abstract Cut<C> withLowerBoundType(BoundType boundType, DiscreteDomain domain);

  abstract Cut<C> withUpperBoundType(BoundType boundType, DiscreteDomain domain);

  abstract void describeAsLowerBound(StringBuilder sb);

  abstract void describeAsUpperBound(StringBuilder sb);

  abstract C leastValueAbove(DiscreteDomain<C> domain);

  abstract C greatestValueBelow(DiscreteDomain<C> domain);

  /*
   * The canonical form is a BelowValue cut whenever possible, otherwise ABOVE_ALL, or
   * (only in the case of types that are unbounded below) BELOW_ALL.
   */
  Cut<C> canonical(DiscreteDomain domain) {
    return this;
  }

  // note: overriden by {BELOW,ABOVE}_ALL
  @Override
  public int compareTo(Cut<C> that) {
    if (that == belowAll()) {
      return 1;
    }
    if (that == aboveAll()) {
      return -1;
    }
    int result = Range.compareOrThrow(endpoint, that.endpoint);
    if (result != 0) {
      return result;
    }
    // same value. below comes before above
    return Booleans.compare(this instanceof AboveValue, that instanceof AboveValue);
  }

  C endpoint() {
    return endpoint;
  }

  @SuppressWarnings("unchecked") // catching CCE
  @Override
  public boolean equals(Object obj) {
    if (obj instanceof Cut) {
      // It might not really be a Cut<C>, but we'll catch a CCE if it's not
      Cut<C> that = (Cut) obj;
      try {
        int compareResult = compareTo(that);
        return compareResult == 0;
      } catch (ClassCastException ignored) {
      }
    }
    return false;
  }

  /*
   * The implementation neither produces nor consumes any non-null instance of type C, so
   * casting the type parameter is safe.
   */
  @SuppressWarnings("unchecked")
  static <C extends Comparable> Cut belowAll() {
    return (Cut<C>) BelowAll.INSTANCE;
  }

  private static final long serialVersionUID = 0;

  private static final class BelowAll extends Cut<Comparable {
    private static final BelowAll INSTANCE = new BelowAll();

    private BelowAll() {
      super(null);
    }

    @Override
    Comparable<?> endpoint() {
      throw new IllegalStateException("range unbounded on this side");
    }

    @Override
    boolean isLessThan(Comparable<?> value) {
      return true;
    }

    @Override
    BoundType typeAsLowerBound() {
      throw new IllegalStateException();
    }

    @Override
    BoundType typeAsUpperBound() {
      throw new AssertionError("this statement should be unreachable");
    }

    @Override
    Cut<Comparable withLowerBoundType(
        BoundType boundType, DiscreteDomain<Comparable domain) {
      throw new IllegalStateException();
    }

    @Override
    Cut<Comparable withUpperBoundType(
        BoundType boundType, DiscreteDomain<Comparable domain) {
      throw new AssertionError("this statement should be unreachable");
    }

    @Override
    void describeAsLowerBound(StringBuilder sb) {
      sb.append("(-\u221e");
    }

    @Override
    void describeAsUpperBound(StringBuilder sb) {
      throw new AssertionError();
    }

    @Override
    Comparable<?> leastValueAbove(DiscreteDomain> domain) {
      return domain.minValue();
    }

    @Override
    Comparable<?> greatestValueBelow(DiscreteDomain> domain) {
      throw new AssertionError();
    }

    @Override
    Cut<Comparable canonical(DiscreteDomain> domain) {
      try {
        return Cut.<ComparablebelowValue(domain.minValue());
      } catch (NoSuchElementException e) {
        return this;
      }
    }

    @Override
    public int compareTo(Cut<Comparable o) {
      return (o == this) ? 0 : -1;
    }

    @Override
    public String toString() {
      return "-\u221e";
    }

    private Object readResolve() {
      return INSTANCE;
    }

    private static final long serialVersionUID = 0;
  }

  /*
   * The implementation neither produces nor consumes any non-null instance of
   * type C, so casting the type parameter is safe.
   */
  @SuppressWarnings("unchecked")
  static <C extends Comparable> Cut aboveAll() {
    return (Cut<C>) AboveAll.INSTANCE;
  }

  private static final class AboveAll extends Cut<Comparable {
    private static final AboveAll INSTANCE = new AboveAll();

    private AboveAll() {
      super(null);
    }

    @Override
    Comparable<?> endpoint() {
      throw new IllegalStateException("range unbounded on this side");
    }

    @Override
    boolean isLessThan(Comparable<?> value) {
      return false;
    }

    @Override
    BoundType typeAsLowerBound() {
      throw new AssertionError("this statement should be unreachable");
    }

    @Override
    BoundType typeAsUpperBound() {
      throw new IllegalStateException();
    }

    @Override
    Cut<Comparable withLowerBoundType(
        BoundType boundType, DiscreteDomain<Comparable domain) {
      throw new AssertionError("this statement should be unreachable");
    }

    @Override
    Cut<Comparable withUpperBoundType(
        BoundType boundType, DiscreteDomain<Comparable domain) {
      throw new IllegalStateException();
    }

    @Override
    void describeAsLowerBound(StringBuilder sb) {
      throw new AssertionError();
    }

    @Override
    void describeAsUpperBound(StringBuilder sb) {
      sb.append("+\u221e)");
    }

    @Override
    Comparable<?> leastValueAbove(DiscreteDomain> domain) {
      throw new AssertionError();
    }

    @Override
    Comparable<?> greatestValueBelow(DiscreteDomain> domain) {
      return domain.maxValue();
    }

    @Override
    public int compareTo(Cut<Comparable o) {
      return (o == this) ? 0 : 1;
    }

    @Override
    public String toString() {
      return "+\u221e";
    }

    private Object readResolve() {
      return INSTANCE;
    }

    private static final long serialVersionUID = 0;
  }

  static <C extends Comparable> Cut belowValue(C endpoint) {
    return new BelowValue<C>(endpoint);
  }

  private static final class BelowValue<C extends Comparable> extends Cut {
    BelowValue(C endpoint) {
      super(checkNotNull(endpoint));
    }

    @Override
    boolean isLessThan(C value) {
      return Range.compareOrThrow(endpoint, value) <= 0;
    }

    @Override
    BoundType typeAsLowerBound() {
      return BoundType.CLOSED;
    }

    @Override
    BoundType typeAsUpperBound() {
      return BoundType.OPEN;
    }

    @Override
    Cut<C> withLowerBoundType(BoundType boundType, DiscreteDomain domain) {
      switch (boundType) {
        case CLOSED:
          return this;
        case OPEN:
          @Nullable C previous = domain.previous(endpoint);
          return (previous == null) ? Cut.<C>belowAll() : new AboveValue(previous);
        default:
          throw new AssertionError();
      }
    }

    @Override
    Cut<C> withUpperBoundType(BoundType boundType, DiscreteDomain domain) {
      switch (boundType) {
        case CLOSED:
          @Nullable C previous = domain.previous(endpoint);
          return (previous == null) ? Cut.<C>aboveAll() : new AboveValue(previous);
        case OPEN:
          return this;
        default:
          throw new AssertionError();
      }
    }

    @Override
    void describeAsLowerBound(StringBuilder sb) {
      sb.append('[').append(endpoint);
    }

    @Override
    void describeAsUpperBound(StringBuilder sb) {
      sb.append(endpoint).append(')');
    }

    @Override
    C leastValueAbove(DiscreteDomain<C> domain) {
      return endpoint;
    }

    @Override
    C greatestValueBelow(DiscreteDomain<C> domain) {
      return domain.previous(endpoint);
    }

    @Override
    public int hashCode() {
      return endpoint.hashCode();
    }

    @Override
    public String toString() {
      return "\\" + endpoint + "/";
    }

    private static final long serialVersionUID = 0;
  }

  static <C extends Comparable> Cut aboveValue(C endpoint) {
    return new AboveValue<C>(endpoint);
  }

  private static final class AboveValue<C extends Comparable> extends Cut {
    AboveValue(C endpoint) {
      super(checkNotNull(endpoint));
    }

    @Override
    boolean isLessThan(C value) {
      return Range.compareOrThrow(endpoint, value) < 0;
    }

    @Override
    BoundType typeAsLowerBound() {
      return BoundType.OPEN;
    }

    @Override
    BoundType typeAsUpperBound() {
      return BoundType.CLOSED;
    }

    @Override
    Cut<C> withLowerBoundType(BoundType boundType, DiscreteDomain domain) {
      switch (boundType) {
        case OPEN:
          return this;
        case CLOSED:
          @Nullable C next = domain.next(endpoint);
          return (next == null) ? Cut.<C>belowAll() : belowValue(next);
        default:
          throw new AssertionError();
      }
    }

    @Override
    Cut<C> withUpperBoundType(BoundType boundType, DiscreteDomain domain) {
      switch (boundType) {
        case OPEN:
          @Nullable C next = domain.next(endpoint);
          return (next == null) ? Cut.<C>aboveAll() : belowValue(next);
        case CLOSED:
          return this;
        default:
          throw new AssertionError();
      }
    }

    @Override
    void describeAsLowerBound(StringBuilder sb) {
      sb.append('(').append(endpoint);
    }

    @Override
    void describeAsUpperBound(StringBuilder sb) {
      sb.append(endpoint).append(']');
    }

    @Override
    C leastValueAbove(DiscreteDomain<C> domain) {
      return domain.next(endpoint);
    }

    @Override
    C greatestValueBelow(DiscreteDomain<C> domain) {
      return endpoint;
    }

    @Override
    Cut<C> canonical(DiscreteDomain domain) {
      C next = leastValueAbove(domain);
      return (next != null) ? belowValue(next) : Cut.<C>aboveAll();
    }

    @Override
    public int hashCode() {
      return ~endpoint.hashCode();
    }

    @Override
    public String toString() {
      return "/" + endpoint + "\\";
    }

    private static final long serialVersionUID = 0;
  }
}