## BJP3 Exercise 17.10: doublePositives

Language/Type: Java binary trees recursion
Author: Robert Baxter (on 2013/04/01)

Write a method `doublePositives` that doubles all data values greater than 0 in a binary tree of integers. For example, the before and after of a call to `doublePositives` on a sample tree are shown below:

Before Call After Call
```            +----+
| -9 |
+----+
/      \
/        \
+----+      +----+
|  3 |      | 15 |
+----+      +----+
/           /      \
/           /        \
+----+      +----+      +----+
|  0 |      | 12 |      | 24 |
+----+      +----+      +----+
/      \
/        \
+----+      +----+
|  6 |      | -3 |
+----+      +----+
```
```            +----+
| -9 |
+----+
/      \
/        \
+----+      +----+
|  6 |      | 30 |
+----+      +----+
/           /      \
/           /        \
+----+      +----+      +----+
|  0 |      | 24 |      | 48 |
+----+      +----+      +----+
/      \
/        \
+----+      +----+
| 12 |      | -3 |
+----+      +----+
```

Assume that you are adding this method to the `IntTree` class as defined below:

```public class IntTree {
private IntTreeNode overallRoot;
...
}
```