Nested Loops

Loops within loops are particularly hard:

public void bubbleSort(int[] nums) {
  for (int i = 0; i < nums.length; ++i) {
    for (int j = 0; j < nums.length - i - 1; ++j) {
      if (nums[j] > nums[j+1]) {
        int temp = nums[j];
	nums[j] = nums[j+1];
	nums[j+1] = temp;
      }
    }
  }
}

The relationship between "i" and "j" is hard to understand

The "nesting" abstraction is tricky; student code could look like this:

public void bubbleSort(int[] nums) {
  for (int i = 0; i < nums.length; ++i) {
  }
  for (int j = 0; j < nums.length; ++j) {
    if (nums[j] > nums[j+1]) {
      int temp = nums[j];
      nums[j] = nums[j+1];
      nums[j+1] = temp;
    }
  }
}

If you assign a nested loop assignment, it might help to give the students the algorithm in English; the student task is reduced to translating English into Java
```
 
For each element i of the array
  For each element j of the array, stopping at size - i
    If j and its successor are out of order, swap them  
```

(next)