Outline of Class 14: Review

Miscellaneous

• Feel free to email me suggestions on these outlines.
• The first Sunday evening dinner went very well. At least one visitor seemed to take thirds on the main course. There are still slots for the coming weeks (the 28th -- meet Michelle; the first weekend in October -- vegetarian).
• Any questions on assignment 3?
• Our first quiz is today. This link will only be active during class.
• But we'll get cookies to eat during the quiz.
• I made significant changes to this outline after class!

this

• Forthcoming

The break statement

• At times, you need to exit your loops (or one repetition of a loop) early.
• For example, you might have noted an abnormal condition, or have reached termination.
• While it is always possible to provide for such early exits by intelligent use of conditionals, such conditionals can inhibit the readability of your code.
• Hence, Java provides methods for exiting loops.
• break exits the current loop (or switch).
• continue exits the current repetition of the loop (going back to the test, and, possibly, to another repetition of the loop).
• Since we often nest loops, Java also provides a mechanism for exiting nested loops. You can label a any of the loops or switches with label: statement and then use break label to break out of that statement. For example

  outer: 
  for (i = 0; i < N; ++i) {
    inner:
    for (j= 0; j < M; ++j) {
      if (meetsCondition(i,j)) {
        System.out.println(
          "Found what we were looking for at (" +
          i + "," + j + ")"
        );
        break outer;
      } // if
    } // inner for loop
    // Here's where you go if you break out of the inner loop
  } // outer for loop
  // Here's where you go if you break out of the outer loop
  

• Similarly, continue can take a label, and returns to the next iteration of the labeled loop.

Exceptions, revisited

An exercise

As a take-home exercise, you are requested to do the following:

• Write a program that uses a for loop.
• See if you can add a finally clause to that loop.
• If so, see what happens when you break out of that loop.
• If you have time, see what happens if you add a finally clause to the inner loop of a pair of nested loops, and break out of the outer loop while in the inner loop.