playground -> putRandom added!

src/PlayGround.java

+import java.util.Random;
+
+public class PlayGround {
+    private int[][] ground;
+    int n, m;
+
+    PlayGround(int n, int m) {
+        this.n = n;
+        this.m = m;
+        ground = new int[n][m];
+        int i, j;
+        for (i = 0; i < n; i++)
+            for (j = 0; j < m; j++)
+                ground[i][j] = 0;
+    }
+
+    public void show() {
+
+    }
+
+    public void putRandom(int policeNumber) {
+        int i, j, k;
+        Random rand = new Random();
+        if (n * m > policeNumber)
+            for (k = 0; k < policeNumber; k++) {
+                i = rand.nextInt();
+                j = rand.nextInt();
+                if (ground[i][j] == 0)
+                    ground[i][j] = 1;
+            else k--;
+            }
+        else System.out.println("Error!! police numbers are higher than n*m");
+    }
+
+
+}