Java 8 functional interfaces - random musings implementing a Scala type

In one of the assignments of the Functional programming with Scala course a type called Terrain is introduced - Terrain represents a region, parts of which are accessible and parts which are not. So in a very clever way Terrain is defined the following way in the assignment:

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case class Pos(x:Int, y: Int)   type Terrain = Pos => Boolean

Essentially Terrain is a function which takes a position and for that position returns a boolean based on whether the position is accessible or not!

Given this definition of Terrain, a way to define an "infinite" terrain where every position is accessible is done this way:

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1	val infiniteTerrain = (pos: Pos) => true

or another terrain, where certain coordinates are accessible can be defined this way:

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def terrainFunction(vector: Vector[Vector[Char]]) : Terrain = {  (pos: Pos) => {   if (pos.x > vector.size - 1 || pos.y > vector(0).size - 1 || pos.x < 0 || pos.y < 0) {    false   } else {    val ch = vector(pos.x)(pos.y)    ch == 'o';   }  } }    val terrain1 = terrainFunction(Vector(      Vector('-','-','-'),      Vector('-','o','-'),      Vector('-','o','-'),      Vector('-','o','-'),      Vector('-','-','-')      )     )

All extremely clever.

Now, given that Java 8 release is imminent, an equally(almost :-) ) clever code can be attempted using Java 8 constructs:

whereas the Terrain could be defined as a function signature in Scala, it has to be defined as a functional interface with Java 8:

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interface Terrain {  public boolean isAccessible(Pos pos); }

Given this interface, an infinite terrain looks like this using Lambdas in Java 8:

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1	Terrain infiniteTerrain = (pos) -> true;

The terrainFunction equivalent in Java 8 can be defined along these lines:

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public Terrain terrainFunction(char[][] arr) {  return (pos) -> {   if (pos.x > arr.length - 1 || pos.y > arr[0].length - 1 || pos.x < 0 || pos.y < 0) {    return false;   } else {    char ch = arr[pos.x][pos.y];    return ch == 'o';   }  }; }    char[][] arr = {  {'-','-','-'},  {'-','o','-'},  {'-','o','-'},  {'-','o','-'},  {'-','-','-'} }; Terrain terrain = terrainFunction(arr);   assertTrue(terrain.isAccessible(new Pos(1, 1)));

Close enough!