lib/java: add some Java collections

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/java/collections.nit b/lib/java/collections.nit
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+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# 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.
+
+# Basic Java collections
+#
+# ~~~
+# var coll = new JavaArray(2)
+#
+# assert coll[0].is_java_null
+# coll[0] = "zero".to_java_string
+# coll[1] = "one".to_java_string
+#
+# assert coll.length == 2
+# assert coll.first.to_s == "zero"
+# assert coll[1].to_s == "one"
+# assert [for e in coll do e.to_s] == ["zero", "one"]
+# ~~~
+module collections
+
+import java
+
+# Java primitive array
+#
+# These have fixed size so they offer the same services as `SequenceRead` and
+# `[]=`, but would not support `Sequence::add`.
+extern class AbstractJavaArray[E: Object]
+       super SequenceRead[E]
+       super JavaObject
+
+       # Set the `value` at `key`
+       fun []=(key: Int, value: E) is abstract
+
+       redef fun iterator do return new JavaArrayIterator[E](self)
+
+       redef fun reverse_iterator do return new JavaArrayReverseIterator[E](self)
+end
+
+# Java primitive array `float[]`
+#
+# Note that Nit `Float` is the size of a double, so storing them in a
+# `JavaFloatArray` may lead to a loss of precision.
+extern class JavaFloatArray in "Java" `{ float[] `}
+       super AbstractJavaArray[Float]
+
+       # Get a new array of the given `size`
+       new(size: Int) in "Java" `{ return new float[(int)size]; `}
+
+       redef fun [](i) in "Java" `{ return (double)recv[(int)i]; `}
+
+       redef fun []=(i, e) in "Java" `{ recv[(int)i] = (float)e; `}
+
+       redef fun length in "Java" `{ return recv.length; `}
+end
+
+# Java primitive array `double[]`
+extern class JavaDoubleArray in "Java" `{ double[] `}
+       super AbstractJavaArray[Float]
+
+       # Get a new array of the given `size`
+       new(size: Int) in "Java" `{ return new double[(int)size]; `}
+
+       redef fun [](i) in "Java" `{ return recv[(int)i]; `}
+
+       redef fun []=(i, e) in "Java" `{ recv[(int)i] = (float)e; `}
+
+       redef fun length in "Java" `{ return recv.length; `}
+end
+
+# Java primitive array `Object[]`
+extern class JavaArray in "Java" `{ java.lang.Object[] `}
+       super AbstractJavaArray[JavaObject]
+
+       # Get a new array of the given `size`
+       new(size: Int) in "Java" `{ return new Object[(int)size]; `}
+
+       redef fun [](i) in "Java" `{ return recv[(int)i]; `}
+
+       redef fun []=(i, e) in "Java" `{ recv[(int)i] = e; `}
+
+       redef fun length in "Java" `{ return recv.length; `}
+end
+
+# TODO other primitive arrays:
+# * Java primitive array `byte[]`
+# * Java primitive array `short[]`
+# * Java primitive array `int[]`
+# * Java primitive array `long[]`
+# * Java primitive array `boolean[]`
+# * Java primitive array `char[]`
+
+# An `Iterator` on Java primitive arrays
+private class JavaArrayIterator[E: Object]
+       super IndexedIterator[E]
+
+       var array: AbstractJavaArray[E]
+
+       redef fun item do return array[index]
+
+       redef fun is_ok do return index < array.length
+
+       redef fun next do index += 1
+
+       redef var index = 0
+end
+
+# A reverse `Iterator` on Java primitive arrays
+private class JavaArrayReverseIterator[E: Object]
+       super IndexedIterator[E]
+
+       var array: AbstractJavaArray[E]
+
+       redef fun item do return array[index]
+
+       redef fun is_ok do return index >= 0
+
+       redef fun next do index -= 1
+
+       redef var index = array.length - 1
+end