October 27, 7:30-9:30 PM Taylor Bacon and Kashif Nazir (Based on slides by Nick Troccoli)

Transcription

1 October 27, 7:30-9:30 PM Taylor Bacon and Kashif Nazir (Based on slides by Nick Troccoli)

2 Topic Date Time Location Assignment 4 Today! Now! Here! Midterm 11/1 7-9PM MemAud Assignment 5 11/9 7:30-9:30PM Hewlett 201 Assignment 6 11/17 7:30-9:30PM Hewlett 201 Assignment 7 12/1 7:30-9:30PM

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4 Your program has crashed!

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7 This is a stack trace. It shows how your code was executed up until it crashed. Here, the last line to run before it crashed was line 19 in Hangman.java

8 Trying to call some method on an object when it is set to null. Passing a null object to a method that will call a method using that object. To fix, check for any variables containing an object (not primitive types like int, double, boolean) that could be null.

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10 You passed a null object as a parameter to one of the Stanford library s methods that can t accept null. You clicked on one of the Stanford library files in a stack trace when debugging E.g. Program.java To fix, check the last line of your code that executed before it reached the Stanford library s methods. Make sure no variable set to null is being passed. Note: Usually, the console will print a stack trace with exactly what exception happened inside the Stanford library. This is a good starting place to see where your code crashed.

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13 Continue either until your code reaches next breakpoint, completes, or crashes.

14 Pause your program at the current line being executed if it is running.

15 Stop your program (this closes the program, unlike pause ).

16 Step into the method being called at the current line. This will pause your code at the first line of the method being called.

17 Step over the method being called at the current line. This will pause your code at the next line.

18 Step out of the method being called at the current line. This will pause your code immediately after the current method completes.

19 View the value of local and instance variables at the current moment.

20 Expand variables to see more details (helpful with objects). Lets you view the values of an object s instance variables.

21 Provides a rough outline for how your code has executed up until the current line (what order were methods called in).

22 Right-Click (or control+click) the blue ribbon at the line you want to add a breakpoint to.

23 Click Toggle Breakpoint to add or remove a breakpoint.

24 Keep track of and easily enable or disable breakpoints.

25 To print output to the debug console, use System.out.println(...) This is helpful for a GraphicsProgram where you can t use println(...)

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29 Person mehran = new Person( Mehran ); mehran.eat(); // Prints out something like nom nom String name = mehran.getname(); // name now contains Mehran

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32 HangmanLexicon lexicon = new HangmanLexicon(); int wordcount = lexicon.getwordcount(); // 10 String word = lexicon.getword(0); // BUOY

33 HangmanLexicon lexicon = new HangmanLexicon(); // triggers HangmanLexicon constructor above

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35 Person mehran = new Person( Mehran ); // triggers Person constructor above

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39 - A list of words (Like a dictionary without definitions) - getwordcount() - getword(i)

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41 char ch = a ; ch = Character.toUpperCase(ch); String str = + ch; // char -> string println(str); Can t just write (for line 2): Character.toUpperCase(ch);

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44 String first = readline( Enter a word: ); String second = readline( Enter another: ); if(character.tolowercase(first.charat(0)) == Character.toLowerCase(second.charAt(0))) { println( The first letters match! ); } else { println( The first letters differ. ); }

45 String s = Hello! ; s = s.touppercase(); println(s); // prints HELLO! Can t just write (for line 2): s.touppercase();

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47 String first = readline( Enter a word: ).tolowercase(); String second = readline( Enter another: ).tolowercase(); If(first.charAt(0) == second.charat(0)) { println( The first letters match! ); } else { println( The first letters differ. ); }

48 String s1 = racecar ; String s2 = reversestring(s1); // How do we check equality? if(s1.equals(s2)) {. } OR if(s2.equals(s1)) {. }

49 String s1 = racecar ; String s2 = reversestring(s1); // How do we check equality? if(s1 == s2) { }

50 indexof indexof indexof int index = hello.indexof( el ); // 1

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59 public void reset() {... } public void displayword(string word) {... } public void noteincorrectguess(char guess) {... }

60 E G N A H C T E N S E DO H T R F O O S Y R N E A T E M S A E R P A Y P T N R U T E R public void reset() {... } public void displayword(string word) {... } public void noteincorrectguess(char guess) {... }

61 private HangmanCanvas canvas;... public void init() { canvas = new HangmanCanvas(); add(canvas); }

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