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Library providing immutable/persistent collection classes for
Java. While collections are immutable they provide methods for
adding and removing values by creating new modified copies of
themselves. Each copy shares almost all of its structure with
other copies to minimize memory consumption.
///###////////////////////////////////////////////////////////////////////////
//
// Burton Computer Corporation
// http://www.burton-computer.com
//
// Copyright (c) 2019, Burton Computer Corporation
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are met:
//
// Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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package org.javimmutable.collections.common;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.Immutable;
import static java.lang.Integer.*;
public abstract class InfiniteKey
implements Comparable
{
static final int CACHE_SIZE = 512;
static final int FLOOR = MIN_VALUE;
static final int LOW = FLOOR + 1;
static final int HIGH = MAX_VALUE;
static InfiniteKey testKey(int... values)
{
InfiniteKey key = values[0] == LOW ? Single.FIRST : new Single(values[0]);
for (int i = 1; i < values.length; ++i) {
key = new Multi(key, values[i]);
}
return key;
}
@Nonnull
public static InfiniteKey first()
{
return Single.FIRST;
}
@Nonnull
public abstract InfiniteKey next();
abstract void addToString(StringBuilder sb);
abstract int value();
@Nonnull
abstract InfiniteKey parent();
@Override
public String toString()
{
final StringBuilder answer = new StringBuilder();
addToString(answer);
return answer.toString();
}
@Override
public int compareTo(@Nonnull InfiniteKey o)
{
if (this == o) {
return 0;
}
int diff = parent().compareTo(o.parent());
if (diff != 0) {
return diff;
}
return Integer.compare(value(), o.value());
}
@Override
public boolean equals(Object obj)
{
if (!(obj instanceof InfiniteKey)) {
return false;
}
return equalTo((InfiniteKey)obj);
}
private boolean equalTo(InfiniteKey o)
{
if (this == o) {
return true;
}
if (value() != o.value()) {
return false;
}
return parent().equalTo(o.parent());
}
private static void stringValue(StringBuilder sb,
int value)
{
sb.append((long)value - (long)LOW);
}
@Immutable
private static class Single
extends InfiniteKey
{
private static final int CACHE_LIMIT;
private static final InfiniteKey[] CACHE;
private static final InfiniteKey STOP;
private static final InfiniteKey FIRST;
static {
STOP = new Single(FLOOR);
CACHE = new InfiniteKey[CACHE_SIZE];
for (int i = 0; i < CACHE_SIZE; ++i) {
CACHE[i] = new Single(LOW + i);
}
FIRST = CACHE[0];
CACHE_LIMIT = LOW + CACHE_SIZE - 1;
}
private final int value;
private Single(int value)
{
this.value = value;
}
@Override
@Nonnull
public InfiniteKey next()
{
if (value == HIGH) {
return new Multi(FIRST, LOW);
}
final int next = value + 1;
if (next <= CACHE_LIMIT) {
return CACHE[next - LOW];
}
return new Single(next);
}
@Override
public int hashCode()
{
return value;
}
@Override
void addToString(StringBuilder sb)
{
stringValue(sb, value);
}
@Override
int value()
{
return value;
}
@Nonnull
@Override
InfiniteKey parent()
{
return STOP;
}
}
@Immutable
private static class Multi
extends InfiniteKey
{
@Nonnull
private final InfiniteKey parent;
private final int value;
private final int hashCode;
private Multi(@Nonnull InfiniteKey parent,
int value)
{
this.value = value;
this.parent = parent;
hashCode = value + 31 * parent.hashCode();
}
@Override
@Nonnull
public InfiniteKey next()
{
if (value == HIGH) {
return new Multi(parent.next(), LOW);
} else {
return new Multi(parent, value + 1);
}
}
@Override
public int hashCode()
{
return hashCode;
}
@Override
void addToString(StringBuilder sb)
{
parent.addToString(sb);
sb.append(".");
stringValue(sb, value);
}
@Override
int value()
{
return value;
}
@Nonnull
@Override
InfiniteKey parent()
{
return parent;
}
}
}