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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.
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///###////////////////////////////////////////////////////////////////////////
//
// Burton Computer Corporation
// http://www.burton-computer.com
//
// Copyright (c) 2021, Burton Computer Corporation
// All rights reserved.
//
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// modification, are permitted provided that the following conditions are met:
//
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// 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
// distribution.
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// of its contributors may be used to endorse or promote products
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//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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package org.javimmutable.collections.indexed;
import org.javimmutable.collections.Indexed;
import javax.annotation.Nonnull;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Function;
/**
* Provides a number of static utility methods for producing Indexed objects
* from raw values. Useful when you need an Indexed but don't have or want
* to create an array just to get an Indexed of them.
*/
public class IndexedHelper
{
private IndexedHelper()
{
}
@Nonnull
public static Indexed empty()
{
return new Indexed()
{
@Override
public T get(int index)
{
throw new ArrayIndexOutOfBoundsException();
}
@Override
public int size()
{
return 0;
}
};
}
/**
* Returns an Indexed containing a single value.
* Note that the type of the Indexed may be a subclass of the type of the value.
*/
@Nonnull
public static Indexed indexed(V a)
{
return new Indexed()
{
@Override
public T get(int index)
{
switch (index) {
case 0:
return a;
default:
throw new ArrayIndexOutOfBoundsException();
}
}
@Override
public int size()
{
return 1;
}
};
}
/**
* Returns an Indexed containing two values.
* Note that the type of the Indexed may be a subclass of the type of the value.
*/
@Nonnull
public static Indexed indexed(V a,
V b)
{
return new Indexed()
{
@Override
public T get(int index)
{
switch (index) {
case 0:
return a;
case 1:
return b;
default:
throw new ArrayIndexOutOfBoundsException();
}
}
@Override
public int size()
{
return 2;
}
};
}
/**
* Returns an Indexed containing three values.
* Note that the type of the Indexed may be a subclass of the type of the value.
*/
@Nonnull
public static Indexed indexed(V a,
V b,
V c)
{
return new Indexed()
{
@Override
public T get(int index)
{
switch (index) {
case 0:
return a;
case 1:
return b;
case 2:
return c;
default:
throw new ArrayIndexOutOfBoundsException();
}
}
@Override
public int size()
{
return 3;
}
};
}
/**
* Returns an Indexed containing three values.
* Note that the type of the Indexed may be a subclass of the type of the value.
*/
@Nonnull
public static Indexed indexed(V a,
V b,
V c,
V... others)
{
final int length = 3 + others.length;
return new Indexed()
{
@Override
public T get(int index)
{
switch (index) {
case 0:
return a;
case 1:
return b;
case 2:
return c;
default:
return others[index - 3];
}
}
@Override
public int size()
{
return length;
}
};
}
@Nonnull
public static Indexed repeating(T value,
int count)
{
return new Indexed()
{
@Override
public T get(int index)
{
if (index < 0 || index >= count) {
throw new ArrayIndexOutOfBoundsException();
} else {
return value;
}
}
@Override
public int size()
{
return count;
}
};
}
@Nonnull
public static Indexed range(int low,
int high)
{
final int size = high - low + 1;
return new Indexed()
{
@Override
public Integer get(int index)
{
if (index < 0 || index >= size) {
throw new ArrayIndexOutOfBoundsException();
}
return low + index;
}
@Override
public int size()
{
return size;
}
};
}
/**
* Creates a mutable List containing all values from the Indexed.
*/
@Nonnull
public static List asList(@Nonnull Indexed indexed)
{
final List answer = new ArrayList<>(indexed.size());
for (int i = 0; i < indexed.size(); ++i) {
answer.add(indexed.get(i));
}
return answer;
}
@Nonnull
public static Indexed transformed(@Nonnull Indexed indexed,
@Nonnull Function transforminator)
{
return new Indexed()
{
@Override
public T get(int index)
{
return transforminator.apply(indexed.get(index));
}
@Override
public int size()
{
return indexed.size();
}
};
}
}