added uebung04 task

uebung04/chess/Board.java

@@ -0,0 +1,54 @@
+package chess;
+
+import java.util.ArrayList;
+
+public class Board {
+  private final Piece[][] field = new Piece[8][8];
+  private final ArrayList<Piece> pieces = new ArrayList<Piece>();
+
+  void add(Piece piece) {
+    if (piece.getBoard() != this)
+      throw new IllegalArgumentException("wrong board");
+    final Piece existing = pieceAt(piece.getRow(), piece.getCol());
+    if (existing != null)
+      throw new IllegalArgumentException("already occupied by " +
+                                         existing.toString());
+    field[piece.getRow() - 1][piece.getCol() - 1] = piece;
+    pieces.add(piece);
+  }
+
+  public void printBoard() {
+    System.out.println("    1   2   3   4   5   6   7   8");
+    System.out.println("  +---+---+---+---+---+---+---+---+");
+    for (int row = 1; row <= 8; row++) {
+      System.out.print("" + row + " ");
+      for (int col = 1; col <= 8; col++) {
+        final Piece p = pieceAt(row, col);
+        final char c = p == null ? ' ' : p.charRep();
+        System.out.print("| " + c + " ");
+      }
+      System.out.println("|");
+      System.out.println("  +---+---+---+---+---+---+---+---+");
+    }
+  }
+
+  public Piece pieceAt(int row, int col) {
+    return field[row - 1][col - 1];
+  }
+
+  public void check() {
+    for (Piece p1 : pieces) {
+      System.out.println(p1.toString());
+      for (Piece p2 : pieces)
+        if (p1 != p2)
+          if (p1.canCapture(p2))
+            System.out.println("   can capture " + p2.toString());
+          else
+            System.out.println("   cannot capture " + p2.toString());
+    }
+  }
+
+  public String toString() {
+    return pieces.toString();
+  }
+}