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Diffstat (limited to 'usth/ICT2.7/P1L3 Integrated Development Environment Subtitles/8 - Eclipse Demo: Debugging - lang_en_vs5.srt')
| -rw-r--r-- | usth/ICT2.7/P1L3 Integrated Development Environment Subtitles/8 - Eclipse Demo: Debugging - lang_en_vs5.srt | 275 |
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diff --git a/usth/ICT2.7/P1L3 Integrated Development Environment Subtitles/8 - Eclipse Demo: Debugging - lang_en_vs5.srt b/usth/ICT2.7/P1L3 Integrated Development Environment Subtitles/8 - Eclipse Demo: Debugging - lang_en_vs5.srt deleted file mode 100644 index 025c2ba..0000000 --- a/usth/ICT2.7/P1L3 Integrated Development Environment Subtitles/8 - Eclipse Demo: Debugging - lang_en_vs5.srt +++ /dev/null @@ -1,275 +0,0 @@ -1 -00:00:00,160 --> 00:00:03,090 -Now let's look at how we can do debugging within - -2 -00:00:03,090 --> 00:00:06,240 -Eclipse. I created a new file called AddNumbers which I'm - -3 -00:00:06,240 --> 00:00:10,770 -showing here. It takes two numbers, parses them into integers, - -4 -00:00:10,770 --> 00:00:14,870 -adds them and prints the sum, supposedly, of the two numbers. - -5 -00:00:14,870 --> 00:00:17,450 -Now we look at the run configuration for this program, - -6 -00:00:17,450 --> 00:00:19,670 -and here you can see that we're passing two arguments, - -7 -00:00:19,670 --> 00:00:22,060 -two and five, to the program. So now let's run - -8 -00:00:22,060 --> 00:00:25,468 -our program and see what happens. And the result says that - -9 -00:00:25,468 --> 00:00:28,150 -2 plus 5 is equal to 10, which is not - -10 -00:00:28,150 --> 00:00:31,030 -exactly correct. So we need to debug our program. We - -11 -00:00:31,030 --> 00:00:33,310 -need to figure out what's wrong with the program, why - -12 -00:00:33,310 --> 00:00:37,140 -the wrong result was, produced. So we're going to add a break - -13 -00:00:37,140 --> 00:00:40,260 -point here by double-clicking here on the side of the - -14 -00:00:40,260 --> 00:00:42,940 -code. And the break point is basically a place where I'm - -15 -00:00:42,940 --> 00:00:46,240 -telling my debugger to stop during the execution because I - -16 -00:00:46,240 --> 00:00:50,750 -want to inspect the state of the program. So to start - -17 -00:00:50,750 --> 00:00:54,690 -debugging, we select Debug as Java Application from the Context - -18 -00:00:54,690 --> 00:00:58,170 -menu, similar to what we were doing for running the program. - -19 -00:00:58,170 --> 00:01:00,190 -And as you can see, this asks us whether we want - -20 -00:01:00,190 --> 00:01:03,720 -to pass to the debug perspective, which is a, a perspective - -21 -00:01:03,720 --> 00:01:07,110 -specifically designed for debugging. We say yes. And as you - -22 -00:01:07,110 --> 00:01:10,750 -see here, it shows us, it's like a different, set of - -23 -00:01:10,750 --> 00:01:13,310 -views, so we can see the code down here with an - -24 -00:01:13,310 --> 00:01:16,100 -indication of where the execution is. And of course the execution - -25 -00:01:16,100 --> 00:01:18,610 -stopped at the break point, which is exactly where - -26 -00:01:18,610 --> 00:01:21,850 -we told the debugger to stop. So let's look at - -27 -00:01:21,850 --> 00:01:24,400 -some of the other views in this perspective. The view - -28 -00:01:24,400 --> 00:01:27,370 -here on the right-hand side, for example, shows the variables - -29 -00:01:27,370 --> 00:01:30,720 -in scope and the break points that are currently active - -30 -00:01:30,720 --> 00:01:33,240 -for the debugging session. This is where the editor is - -31 -00:01:33,240 --> 00:01:36,710 -at. The outline of the program and the console at - -32 -00:01:36,710 --> 00:01:41,520 -the bottom. So now let's execute one line by clicking - -33 -00:01:41,520 --> 00:01:45,400 -on the Step Over button here at the top, and this will - -34 -00:01:45,400 --> 00:01:49,150 -execute the line that is currently highlighted and therefore it will move to - -35 -00:01:49,150 --> 00:01:51,500 -the next line. And as you can see, one nice feature is that - -36 -00:01:51,500 --> 00:01:54,760 -if I move the mouse over a variable, I can see the value - -37 -00:01:54,760 --> 00:01:57,710 -of the variable. And the same thing I can do if I look - -38 -00:01:57,710 --> 00:02:00,690 -at the variables windows here on the right. If I click it, it - -39 -00:02:00,690 --> 00:02:03,960 -will tell me what is the value of the variable, and in case - -40 -00:02:03,960 --> 00:02:07,410 -of more complex variables you can even expand it and get more details. - -41 -00:02:07,410 --> 00:02:10,870 -So now let's step over another line by clicking again this button, - -42 -00:02:10,870 --> 00:02:13,180 -and as you can see now we get to the line that - -43 -00:02:13,180 --> 00:02:16,410 -is actually performing the sum, supposedly, so now let's do the same - -44 -00:02:16,410 --> 00:02:19,100 -thing that we did before, and let's mouse over b, and we can - -45 -00:02:19,100 --> 00:02:22,150 -see that the value of b is five, as expected. So now - -46 -00:02:22,150 --> 00:02:27,080 -let's step over this line as well, and execute the actual sum. And - -47 -00:02:27,080 --> 00:02:29,730 -doing the mouseover thing, we can see that the value of sum - -48 -00:02:29,730 --> 00:02:33,000 -is ten, which is not right, of course. In fact, if we check - -49 -00:02:33,000 --> 00:02:35,590 -a gain we can see that value of A is two. The - -50 -00:02:35,590 --> 00:02:39,130 -value of B is five and therefore it's clear that there's something - -51 -00:02:39,130 --> 00:02:41,780 -wrong going on here, and at this point we can notice that - -52 -00:02:41,780 --> 00:02:44,030 -here we are doing multiplication instead - -53 -00:02:44,030 --> 00:02:46,010 -of addition. And therefore that's what the - -54 -00:02:46,010 --> 00:02:49,260 -error is. And this is clearly a very simple case. Right? A - -55 -00:02:49,260 --> 00:02:51,440 -case in which probably you just needed to look at the code and - -56 -00:02:51,440 --> 00:02:54,150 -you didn't need the debugger. But you probably got the idea right? - -57 -00:02:54,150 --> 00:02:58,055 -So this can be extremely useful when you're debugging, when you're studying more - -58 -00:02:58,055 --> 00:03:01,533 -complex programs. If you want to stop the debugger because you're - -59 -00:03:01,533 --> 00:03:04,557 -done with your debugging session as in this case, you can - -60 -00:03:04,557 --> 00:03:07,518 -either click here on the Terminate button or you can also - -61 -00:03:07,518 --> 00:03:11,109 -just simply tell the debugger to continue the execution, to resume - -62 -00:03:11,109 --> 00:03:15,140 -the execution until the program terminates naturally. So, in this case, - -63 -00:03:15,140 --> 00:03:17,520 -we're going to click here just to show what happens. And what - -64 -00:03:17,520 --> 00:03:20,230 -happens is that, you know, the execution will just continue until - -65 -00:03:20,230 --> 00:03:23,690 -the program exits. So now let's say that we want to fix - -66 -00:03:23,690 --> 00:03:27,740 -this problem that we just discovered. So we replace the multiplication - -67 -00:03:27,740 --> 00:03:30,600 -with an addition, we save the program, and we execute the - -68 -00:03:30,600 --> 00:03:33,860 -program again by clicking on this button. And at this point, - -69 -00:03:33,860 --> 00:03:37,320 -unsurprisingly, we get the right result as shown in the console. |