This video shows the runtime error that results when an index references beyond the end of an array. IT points out that one should always look both at the line number in a runtime error and the index listed in an ArrayIndexOutOfBounds error. This error is fixed by changing the constant index values which are used to index the array.

This video shows the problem of code that doesn’t produce the correct output because the loop has an off-by-one error when it processes the array to find an average.

This video shows the incorrect uses of || (or) in a compound boolean expression to control a validation loop. The incorrect boolean expression matches with commonly used English “if the user doesn’t answer ‘yes’ or the user doesn’t answer ‘no’ then make them type in another answer.” This expression is complicated by the fact that the “not” is used in conjunction with .equals is harder to parse than, for example, !=.

A program that generates “illegal start of type” and “ expected” error although the code looks OK.

What to do when you see an incompatible types compiler error in a loop condition or in the condition of an if statement.

Shows the effect of using equals (=) instead of equalsequals (==), causing an assignment when you intend to have a equality comparison.

What to do when you see an incompatible types compiler error in a loop condition or in the condition of an if statement.

Shows the effect of using equals (=) instead of equalsequals (==), causing an assignment when you intend to have a equality comparison.

Shows an infinite loop that occurs due to lack of update of a loop iterator inside an if statement in the loop. It identifies that an infinite loop is happening when the program does not seem to end. It then shows how to insert print statements to output the iterator value at the beginning of the loop, and then again at the end of the loop.

Shows an infinite loop that occurs due to lack of update of a loop iterator inside an if statement in the loop. It identifies that an infinite loop is happening when the program does not seem to end. It then shows how to insert print statements to output the iterator value at the beginning of the loop, and then again at the end of the loop.

Shows what happens when a local variable in a method has the same name as an instance variable in your class and provides 2 ways to fix this problem (instance variable masking).

A short tutorial on working with string methods and dealing with the return value. Demonstration of the String substring and toUppercase methods.

This video demonstrates a logic error where the program runs to completion, but produces the wrong output. The process of identifying, finding, and fixing the error is modeled. The error stems from the incorrect use of a formula to control the parameters of the subString method. The code attempts to throw away occurrences of the strings “cat” and “dog” as they are counted – but makes a mistake in doing so. The code is analyzed, corrected, and tested.

This video shows a program which is searching through an array, in a linear fashion, looking for a value. It has an if…else statement within a loop which assigns a boolean value to a variable called “found” every iteration of the loop (if theArray[index] == value). It shows that the code works for any value not in the array, but that it always reports “found” to be false, even for values that are in the array. By inserting print statements at the start of the if block and then in the else block, it shows that “found” is updated every iteration of the loop, potentially overwriting the assignment of true to “found.”

This video shows an infinite loop that occurs due to a lack of an input statement inside a validation loop. A prompt and a scan is used before the loop, but the code inside the loop only has a prompt. It points out the infinite loop and shows the addition of a read statement to fix the problem.

Small method demonstrating syntax error caused by a missing semi-colon.

This video shows the problem of trying to return a value calculated in a method through a parameter, where the student is assuming that Java parameters are passed by reference. The video shows the process of returning two values from a method and how this can be accomplished with an array.