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/*
* 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.CheckForNull;
/**
* 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
@ElementTypesAreNonnullByDefault
abstract class Cut implements Comparable>, Serializable {
final C endpoint;
Cut(C endpoint) {
this.endpoint = endpoint;
}
abstract boolean isLessThan(C value);
abstract BoundType typeAsLowerBound();
abstract BoundType typeAsUpperBound();
abstract Cut withLowerBoundType(BoundType boundType, DiscreteDomain domain);
abstract Cut withUpperBoundType(BoundType boundType, DiscreteDomain domain);
abstract void describeAsLowerBound(StringBuilder sb);
abstract void describeAsUpperBound(StringBuilder sb);
@CheckForNull
abstract C leastValueAbove(DiscreteDomain domain);
@CheckForNull
abstract C greatestValueBelow(DiscreteDomain 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 canonical(DiscreteDomain domain) {
return this;
}
// note: overridden by {BELOW,ABOVE}_ALL
@Override
public int compareTo(Cut 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(@CheckForNull Object obj) {
if (obj instanceof Cut) {
// It might not really be a Cut, but we'll catch a CCE if it's not
Cut that = (Cut) obj;
try {
int compareResult = compareTo(that);
return compareResult == 0;
} catch (ClassCastException wastNotComparableToOurType) {
return false;
}
}
return false;
}
// Prevent "missing hashCode" warning by explicitly forcing subclasses implement it
@Override
public abstract int hashCode();
/*
* The implementation neither produces nor consumes any non-null instance of type C, so
* casting the type parameter is safe.
*/
@SuppressWarnings("unchecked")
static Cut belowAll() {
return (Cut) BelowAll.INSTANCE;
}
private static final long serialVersionUID = 0;
private static final class BelowAll extends Cut> {
private static final BelowAll INSTANCE = new BelowAll();
private BelowAll() {
/*
* No code ever sees this bogus value for `endpoint`: This class overrides both methods that
* use the `endpoint` field, compareTo() and endpoint(). Additionally, the main implementation
* of Cut.compareTo checks for belowAll before reading accessing `endpoint` on another Cut
* instance.
*/
super("");
}
@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> withLowerBoundType(
BoundType boundType, DiscreteDomain> domain) {
throw new IllegalStateException();
}
@Override
Cut> withUpperBoundType(
BoundType boundType, DiscreteDomain> 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> canonical(DiscreteDomain> domain) {
try {
return Cut.>belowValue(domain.minValue());
} catch (NoSuchElementException e) {
return this;
}
}
@Override
public int compareTo(Cut> o) {
return (o == this) ? 0 : -1;
}
@Override
public int hashCode() {
return System.identityHashCode(this);
}
@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 Cut aboveAll() {
return (Cut) AboveAll.INSTANCE;
}
private static final class AboveAll extends Cut> {
private static final AboveAll INSTANCE = new AboveAll();
private AboveAll() {
// For discussion of "", see BelowAll.
super("");
}
@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> withLowerBoundType(
BoundType boundType, DiscreteDomain> domain) {
throw new AssertionError("this statement should be unreachable");
}
@Override
Cut> withUpperBoundType(
BoundType boundType, DiscreteDomain> 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> o) {
return (o == this) ? 0 : 1;
}
@Override
public int hashCode() {
return System.identityHashCode(this);
}
@Override
public String toString() {
return "+\u221e";
}
private Object readResolve() {
return INSTANCE;
}
private static final long serialVersionUID = 0;
}
static Cut belowValue(C endpoint) {
return new BelowValue<>(endpoint);
}
private static final class BelowValue 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 withLowerBoundType(BoundType boundType, DiscreteDomain domain) {
switch (boundType) {
case CLOSED:
return this;
case OPEN:
C previous = domain.previous(endpoint);
return (previous == null) ? Cut.belowAll() : new AboveValue(previous);
default:
throw new AssertionError();
}
}
@Override
Cut withUpperBoundType(BoundType boundType, DiscreteDomain domain) {
switch (boundType) {
case CLOSED:
C previous = domain.previous(endpoint);
return (previous == null) ? Cut.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 domain) {
return endpoint;
}
@Override
@CheckForNull
C greatestValueBelow(DiscreteDomain 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 Cut aboveValue(C endpoint) {
return new AboveValue<>(endpoint);
}
private static final class AboveValue 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 withLowerBoundType(BoundType boundType, DiscreteDomain domain) {
switch (boundType) {
case OPEN:
return this;
case CLOSED:
C next = domain.next(endpoint);
return (next == null) ? Cut.belowAll() : belowValue(next);
default:
throw new AssertionError();
}
}
@Override
Cut withUpperBoundType(BoundType boundType, DiscreteDomain domain) {
switch (boundType) {
case OPEN:
C next = domain.next(endpoint);
return (next == null) ? Cut.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
@CheckForNull
C leastValueAbove(DiscreteDomain domain) {
return domain.next(endpoint);
}
@Override
C greatestValueBelow(DiscreteDomain domain) {
return endpoint;
}
@Override
Cut canonical(DiscreteDomain domain) {
C next = leastValueAbove(domain);
return (next != null) ? belowValue(next) : Cut.aboveAll();
}
@Override
public int hashCode() {
return ~endpoint.hashCode();
}
@Override
public String toString() {
return "/" + endpoint + "\\";
}
private static final long serialVersionUID = 0;
}
}