diff -r f1d7de36b01e -r 5179eff8a9b6 src/de/uapcore/sudoku/Solver.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/de/uapcore/sudoku/Solver.java	Sat Jan 26 17:42:07 2013 +0100
@@ -0,0 +1,122 @@
+package de.uapcore.sudoku;
+
+/**
+ *
+ * @author mike
+ */
+public final class Solver {
+    
+    public Solver() {
+    }
+    
+    public boolean check(Field f) {
+        int line[];
+        for (int i = 0 ; i < 9 ; i++) {
+            line = getRow(f, i);
+            if (!valid(line)) {
+                return false;
+            }
+            line = getColumn(f, i);
+            if (!valid(line)) {
+                return false;
+            }
+        }
+        
+        int square[][];
+        for (int x = 0 ; x < 3 ; x++) {
+            for (int y = 0 ; y < 3 ; y++) {
+                square = getSquare(f, x, y);
+                if (!valid(square)) {
+                    return false;
+                }
+            }
+        }
+        
+        return true;
+    }
+    
+    private boolean complete(int[][] square) {
+        for (int x = 0 ; x < 3 ; x++) {
+            for (int y = 0 ; y < 3 ; y++) {
+                if (square[x][y] == 0) {
+                    return false;
+                }
+            }    
+        }
+        return true;
+    }
+    
+    private boolean complete(int[] line) {
+        for (int i = 0 ; i < 9 ; i++) {
+            if (line[i] == 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+    
+    private boolean valid(int[] line) {
+        int numbers[] = new int[9];
+        for (int i = 0 ; i < 9 ; i++) {
+            int l = line[i]-1;
+            if (l >= 0) {
+                if (++numbers[l] > 1) {
+                    return false;
+                }
+            }
+        }
+        
+        return true;
+    }
+    
+    private boolean valid(int[][] square) {
+        int[] line = new int[9];
+        for (int x = 0 ; x < 3 ; x++) {
+            for (int y = 0 ; y < 3 ; y++) {
+                line[3*x+y] = square[x][y];
+            }    
+        }
+        return valid(line);
+    }
+    
+    private int[][] getSquare(Field f, int x, int y) {
+        if (x < 0 || x > 2 || y < 0 || y > 2) {
+            throw new IllegalArgumentException("Invalid square coordinates");
+        }
+        int[][] square = new int[3][3];
+        
+        for (int u = 0 ; u < 3 ; u++) {
+            for (int v = 0 ; v < 3 ; v++) {
+                square[u][v] = f.getCellValue(3*x+u, 3*y+v);
+            }
+        }
+        
+        return square;
+    }
+    
+    private int[] getRow(Field f, int y) {
+        if (y < 0 || y > 8) {
+            throw new IllegalArgumentException("Invalid row number");
+        }
+        int row[] = new int[9];
+        
+        for (int x = 0 ; x < 9 ; x++) {
+            row[x] = f.getCellValue(x, y);
+        }
+        
+        return row;
+    }
+    
+    private int[] getColumn(Field f, int x) {
+        if (x < 0 || x > 8) {
+            throw new IllegalArgumentException("Invalid column number");
+        }
+        int column[] = new int[9];
+        
+        for (int y = 0 ; y < 9 ; y++) {
+            column[y] = f.getCellValue(x, y);
+        }
+        
+        return column;
+    }
+}