WEBVTT 1 00:00:00.080 --> 00:00:03.000 Have you ever been deep in Minecraft, maybe building something 2 00:00:03.000 --> 00:00:06.960 amazing and just thought, man, I wish this worked differently. 3 00:00:07.240 --> 00:00:11.960 Oh, definitely, like wanting a custom command, or maybe changing 4 00:00:12.000 --> 00:00:12.960 how blocks. 5 00:00:12.599 --> 00:00:15.279 Behave exactly Like, would it be cool to type one 6 00:00:15.320 --> 00:00:17.440 thing and have I don't know, a whole army pop up, 7 00:00:18.000 --> 00:00:20.239 or maybe make every block you touch turn to gold. 8 00:00:20.440 --> 00:00:23.320 Yeah. Taking that world you know so well and then 9 00:00:23.359 --> 00:00:27.839 getting the power to actually tweak the rules with code. Well, 10 00:00:28.280 --> 00:00:29.760 it's literally a game changer. 11 00:00:29.760 --> 00:00:32.240 It really is. And that's that's pretty much what this 12 00:00:32.280 --> 00:00:34.600 deep dive is all about. Today. We've been looking at 13 00:00:34.600 --> 00:00:39.200 this beginner's guide that focuses specifically on using Java programming 14 00:00:39.439 --> 00:00:41.359 to make those custom Minecraft mods. 15 00:00:41.799 --> 00:00:44.679 Yeah, think of this as a bit of a shortcut. 16 00:00:45.000 --> 00:00:47.880 We're aiming to unpack the core bits of Java you 17 00:00:47.920 --> 00:00:51.000 really need and show how they plug directly into making 18 00:00:51.039 --> 00:00:53.240 your own mods, you know, going from just playing the 19 00:00:53.240 --> 00:00:54.600 game to actually shaping it. 20 00:00:54.679 --> 00:00:57.840 Okay, so let's start right at the beginning. Why Java? 21 00:00:58.200 --> 00:00:59.880 Why is that the language for Minecraft? 22 00:01:00.799 --> 00:01:03.439 Well, the source material is pretty clear on this. Minecraft 23 00:01:03.439 --> 00:01:06.280 itself is built using Java, so it just makes sense. 24 00:01:06.319 --> 00:01:09.239 It's the native tongue, if you will. And importantly, the 25 00:01:09.239 --> 00:01:13.280 guide really emphasizes that it's not some super scary, impossible 26 00:01:13.359 --> 00:01:16.560 language to pick up, especially just for modding basics. 27 00:01:16.799 --> 00:01:19.719 That's encouraging. So what tools do you actually need to 28 00:01:19.760 --> 00:01:20.239 get going? 29 00:01:20.519 --> 00:01:25.200 It's surprisingly accessible really. First you need the Java development kit, 30 00:01:25.319 --> 00:01:27.439 the cord Java stuff itself, it's free. 31 00:01:27.719 --> 00:01:28.040 Okay. 32 00:01:28.159 --> 00:01:30.159 Then you need a place to write the code. The 33 00:01:30.159 --> 00:01:33.159 guide recommends net beans. That beans right, Yeah, it's an 34 00:01:33.200 --> 00:01:37.480 ID and integrated development environment, basically a smart text editor 35 00:01:37.519 --> 00:01:38.959 for code. Also free. 36 00:01:39.200 --> 00:01:42.400 So Java net beans. Huh what else do you need? 37 00:01:42.400 --> 00:01:43.519 The game? Ah? 38 00:01:43.640 --> 00:01:48.000 Yes, you definitely need the actual Minecraft game client, specifically, 39 00:01:48.040 --> 00:01:51.000 the guide mentions the Windows or mac os versions. That's 40 00:01:51.040 --> 00:01:54.000 the paid part around twenty seven dollars currently. 41 00:01:53.640 --> 00:01:55.799 And that's where you'll actually see your mod in action. 42 00:01:56.000 --> 00:01:57.959 Well, you need one more piece for testing, according to 43 00:01:57.959 --> 00:02:00.760 the guide, a Minecraft server you set up, usually on 44 00:02:00.799 --> 00:02:03.799 your own machine, to start your own little test world exactly. 45 00:02:03.920 --> 00:02:06.959 Your mod runs on the server, and then you connect 46 00:02:07.000 --> 00:02:10.039 to that server with your regular Minecraft game client using 47 00:02:10.080 --> 00:02:14.360 the multiplayer option. That whole setup is your development and 48 00:02:14.439 --> 00:02:15.400 testing playground. 49 00:02:15.520 --> 00:02:19.039 Okay, setup complete, Now let's crack open NetBeans. You've got 50 00:02:19.039 --> 00:02:21.680 this software. Yeah, where do you even click? First. 51 00:02:22.000 --> 00:02:25.479 Right, So in NetBeans, you typically start by creating a 52 00:02:25.520 --> 00:02:26.879 new project. 53 00:02:27.039 --> 00:02:29.919 A project like a folder for the mod pretty much. 54 00:02:30.000 --> 00:02:32.520 Yeah, it holds all the files related to that specific 55 00:02:32.560 --> 00:02:35.960 mod you're building. And inside that project, you create a 56 00:02:36.000 --> 00:02:37.840 new Java class file, and the. 57 00:02:37.840 --> 00:02:39.759 Class file is where the actual instructions go. 58 00:02:39.879 --> 00:02:42.280 It's it. It's like a blueprint. You write your Java code, 59 00:02:42.280 --> 00:02:44.319 your instructions inside that class file. 60 00:02:44.400 --> 00:02:48.439 Now, for the program to actually well run, it needs 61 00:02:48.479 --> 00:02:51.800 a specific starting point, doesn't it like computers start here exactly? 62 00:02:52.039 --> 00:02:55.319 Every standalone Java program that you can just run needs 63 00:02:55.319 --> 00:02:58.400 a special method called main. Okay, that's the entry point. 64 00:02:58.400 --> 00:03:00.680 When you hit run, the java is looks for that 65 00:03:00.759 --> 00:03:03.800 main method first and starts executing the code inside it. 66 00:03:03.879 --> 00:03:06.479 The guide had that classic first example, right. The im 67 00:03:06.520 --> 00:03:07.319 spartakan is one. 68 00:03:07.680 --> 00:03:11.680 Yeah, you type one line of code inside Maine something 69 00:03:11.800 --> 00:03:16.520 like system out dot printle nimspartacus. You run it in 70 00:03:16.639 --> 00:03:17.680 net Beans. 71 00:03:17.599 --> 00:03:20.000 And bam, it appears in the output window. 72 00:03:20.159 --> 00:03:23.319 Yep, your first little piece of running code. It's a 73 00:03:23.319 --> 00:03:25.520 good feeling, But coding. 74 00:03:25.240 --> 00:03:29.520 Isn't always smooth sailing. What about mistakes? Typos? 75 00:03:29.719 --> 00:03:33.560 Ah? Yes, errors. The guide jumps right into that. It's 76 00:03:33.599 --> 00:03:36.439 just good. It shows how NetBeans helps you out immediately 77 00:03:37.240 --> 00:03:40.199 how so well, say you forget a semicolon at the 78 00:03:40.240 --> 00:03:42.360 end of a line, which is easy to do. Net 79 00:03:42.360 --> 00:03:44.639 Beans will often put a little red squiggle under it 80 00:03:45.039 --> 00:03:46.159 or show an error. 81 00:03:46.159 --> 00:03:47.840 Icon like spell check for code. 82 00:03:48.000 --> 00:03:50.680 Kind of yeah, it gives you instant feedback telling you, hey, 83 00:03:50.719 --> 00:03:53.400 something's not quite right here. It really helps catch simple 84 00:03:53.439 --> 00:03:54.240 mistakes early. 85 00:03:54.560 --> 00:03:58.039 That sounds super useful for beginners. The guide also mentioned 86 00:03:58.080 --> 00:04:00.560 comments lines that aren't actually right. 87 00:04:00.840 --> 00:04:03.800 Comments you start them with for a single line, or 88 00:04:04.000 --> 00:04:05.639 wrap a block with an NM, and. 89 00:04:05.599 --> 00:04:07.120 The computer just ignores them. 90 00:04:07.000 --> 00:04:10.039 Completely ignores them when running the program. But they're absolutely 91 00:04:10.199 --> 00:04:13.400 vital for humans for understanding what you wrote later exactly, 92 00:04:13.520 --> 00:04:16.240 or for someone else reading your code. They're like little 93 00:04:16.279 --> 00:04:19.519 notes explaining why you did something or what a particular 94 00:04:19.560 --> 00:04:23.279 section of code is trying to achieve. Essential for anything complex. 95 00:04:23.519 --> 00:04:27.199 Okay, so we can run a basic instruction, but mods 96 00:04:27.279 --> 00:04:32.600 need to remember things right, like a player's name or coordinates, 97 00:04:33.240 --> 00:04:36.600 or maybe how much health a mob has. How does 98 00:04:36.680 --> 00:04:37.600 Java handle that? 99 00:04:37.600 --> 00:04:40.000 That's where variables come in. You can think of variables 100 00:04:40.000 --> 00:04:43.600 as named containers, like little labeled boxes in the computer's memory. 101 00:04:43.680 --> 00:04:46.560 Boxes to store information precisely. 102 00:04:46.040 --> 00:04:48.519 You put pieces of data into these boxes so you 103 00:04:48.519 --> 00:04:49.920 can use them later in your mod. 104 00:04:50.160 --> 00:04:52.439 And these boxes hold different kinds of information. 105 00:04:52.600 --> 00:04:56.480 Yes, very important variables have types for Minecraft moding. The 106 00:04:56.560 --> 00:04:58.839 guide highlights a few key ones. You'll use a lot 107 00:04:59.199 --> 00:05:01.639 like well, is a big one. That's for whole numbers, 108 00:05:01.800 --> 00:05:04.560 think coordinates xyz or counting items. 109 00:05:04.319 --> 00:05:06.399 Stuff like that. Okay, in for whole numbers. 110 00:05:06.439 --> 00:05:10.160 Then there's string note the capital s. That's for storing text, 111 00:05:10.399 --> 00:05:12.800 player names, messages you want to show in chat command 112 00:05:12.879 --> 00:05:14.720 words like stone or diamond. 113 00:05:14.879 --> 00:05:18.240 So inf counts string for text. Makes sense. 114 00:05:18.360 --> 00:05:21.079 The guide also mentions float and double for numbers with 115 00:05:21.160 --> 00:05:24.360 decimal points maybe for precise positions or something, and char 116 00:05:24.480 --> 00:05:27.759 for just a single character. But honestly, int and string 117 00:05:27.839 --> 00:05:30.560 will get you very far when you're starting out with mods. 118 00:05:30.920 --> 00:05:34.439 How do you like create one of these variable boxes? 119 00:05:34.480 --> 00:05:36.639 You declare it. You see the type, then the name 120 00:05:36.680 --> 00:05:39.399 you want to give it. So int player score creates 121 00:05:39.399 --> 00:05:40.920 an integer variable named. 122 00:05:40.800 --> 00:05:42.920 Player score, and putting a value in it. 123 00:05:42.800 --> 00:05:45.439 You use the equal sign. That's the assignment operator. So 124 00:05:45.519 --> 00:05:48.639 player score equals one hundred, puts the value one hundred 125 00:05:48.639 --> 00:05:49.360 into that box. 126 00:05:49.480 --> 00:05:51.519 The guide also showed some shortcuts, didn't. 127 00:05:51.279 --> 00:05:54.920 It, Like plus Yeah, player score plus ten is shorthand 128 00:05:54.920 --> 00:05:57.800 for player score player score plus ten and plus plus 129 00:05:57.800 --> 00:06:00.240 act like player score plus plus ac just adds one 130 00:06:00.600 --> 00:06:02.000 very common, saves a bit of typing. 131 00:06:02.120 --> 00:06:04.800 Are the rules for naming these variables A few simple ones. 132 00:06:05.040 --> 00:06:07.639 They are case sensitive, so player score is different from 133 00:06:07.639 --> 00:06:11.319 player score. Okay, no spaces or punctuation usually allowed in 134 00:06:11.360 --> 00:06:15.800 the name, and you can't use java's reserve words words 135 00:06:15.879 --> 00:06:20.120 like public class INNT if those already have special meanings. 136 00:06:20.279 --> 00:06:23.879 Got it. So variables hold the data, What about doing 137 00:06:23.920 --> 00:06:24.959 things with that data? 138 00:06:25.560 --> 00:06:29.279 Calculations, right, That's where expressions and operators come in. You 139 00:06:29.399 --> 00:06:34.240 use operators like plus for addition, for subtraction, for a multiplication. 140 00:06:33.720 --> 00:06:35.439 For division, just like basic math. 141 00:06:35.519 --> 00:06:38.360 Pretty much in total score at score one plus score 142 00:06:38.399 --> 00:06:42.759 two adds two scores together. The guide mentions operator precedence 143 00:06:42.839 --> 00:06:47.439 like multiplication happens before addition, and this exactly. But you 144 00:06:47.439 --> 00:06:50.040 can always use parentheses to control the order, just like 145 00:06:50.079 --> 00:06:52.600 in math class to make sure things calculate the way 146 00:06:52.600 --> 00:06:53.160 you intend. 147 00:06:53.439 --> 00:06:55.720 And once you've done a calculation, or you just want 148 00:06:55.759 --> 00:06:57.800 to display some text, how do you show that to 149 00:06:57.839 --> 00:06:59.879 the user or maybe in the serverlog. 150 00:07:00.079 --> 00:07:03.439 The most fundamental way in Java is using system dot 151 00:07:03.480 --> 00:07:04.920 out dot print allen. 152 00:07:05.120 --> 00:07:07.279 System dot out dot print allen. Bit of a. 153 00:07:07.199 --> 00:07:09.519 Mouthful, it is, but you get used to it. Whatever 154 00:07:09.560 --> 00:07:12.279 you put inside the parentheses gets printed out, usually to 155 00:07:12.319 --> 00:07:15.079 the NetBeans output window or the Micraft server console. When 156 00:07:15.079 --> 00:07:16.079 you're moddling like. 157 00:07:16.079 --> 00:07:18.759 That example, alphae has been killed by a magma cube. 158 00:07:18.839 --> 00:07:22.399 Huh huh, yeah, that memorable one, that exact text would appear. 159 00:07:22.680 --> 00:07:25.519 There's also system dot out dot print, which does the 160 00:07:25.519 --> 00:07:28.279 same thing, but doesn't automatically start a new line afterwards. 161 00:07:28.360 --> 00:07:30.839 Okay, so we can store info, do math, print stuff out. 162 00:07:31.759 --> 00:07:35.199 But real programs need to make decisions, don't they Like 163 00:07:35.560 --> 00:07:39.839 if the player does X, then do HY or repeat tasks. 164 00:07:40.000 --> 00:07:42.720 Absolutely, that's control flow. You need ways to control which 165 00:07:42.759 --> 00:07:46.079 lines of code execute and when. Conditional statements and loops 166 00:07:46.120 --> 00:07:47.000 are the pills for that. 167 00:07:47.319 --> 00:07:49.720 Conditionals first making choices. 168 00:07:50.000 --> 00:07:52.120 The simplest is the if statement. You give it a 169 00:07:52.120 --> 00:07:54.759 condition something that's either true or false. If it's true, 170 00:07:54.759 --> 00:07:57.759 the code inside the if block runs. If not, it's skipped. 171 00:07:57.879 --> 00:08:00.959 So if player has enough gold, then run the code 172 00:08:01.000 --> 00:08:02.399 to give them the item exactly. 173 00:08:02.399 --> 00:08:04.879 Then you've got if else. This gives you two paths. 174 00:08:04.920 --> 00:08:07.160 If the condition is true, do the if part. If 175 00:08:07.199 --> 00:08:09.560 it falls else, do the else part. Plan A, plan B. 176 00:08:10.160 --> 00:08:13.079 The guide also mentioned the switch statement. That's useful when 177 00:08:13.120 --> 00:08:15.120 you have one value and you want to do different 178 00:08:15.160 --> 00:08:18.319 things based on several possible specific values. It could have 179 00:08:18.839 --> 00:08:21.439 like checking an item type and doing something different for 180 00:08:21.480 --> 00:08:23.439 a sword, an ax, or a pick axe. 181 00:08:23.480 --> 00:08:27.319 Okay, decisions covered. What about doing things repeatedly? 182 00:08:27.519 --> 00:08:33.240 Loops essential for so many modding tasks. Imagine placing blocks 183 00:08:33.279 --> 00:08:36.279 in a line or checking every slot in a chest. 184 00:08:36.440 --> 00:08:37.240 You need loops. 185 00:08:37.440 --> 00:08:38.840 The fore loop is one, right, Yeah. 186 00:08:38.879 --> 00:08:41.440 The fore loop is often used when you know roughly 187 00:08:41.559 --> 00:08:44.200 how many times you need to repeat something. You typically 188 00:08:44.240 --> 00:08:46.399 set up a counter, tell it when to stop and 189 00:08:46.440 --> 00:08:47.720 how to increment. 190 00:08:47.600 --> 00:08:50.039 Like for I from zero to nine place. 191 00:08:49.799 --> 00:08:52.879 A block perfect example. Then there's the wil loop. It's different. 192 00:08:52.919 --> 00:08:56.159 It keeps looping as long as a condition stays true. 193 00:08:56.080 --> 00:08:58.759 More like while the button is held down, keep doing 194 00:08:58.799 --> 00:08:59.720 this exactly. 195 00:09:00.080 --> 00:09:02.960 The condition is checked before each loop iteration. The guide 196 00:09:03.000 --> 00:09:06.080 also mentions do while, which is similar, but the check 197 00:09:06.120 --> 00:09:09.200 happens after the code runs, so it always runs at least. 198 00:09:08.960 --> 00:09:11.039 Once, and sometimes you need to stop a loop early. 199 00:09:11.399 --> 00:09:13.639 Yeah, the break statement lets you jump out of a 200 00:09:13.679 --> 00:09:16.399 loop immediately. If you're searching through a list and find 201 00:09:16.399 --> 00:09:18.360 the item you need on the third try, you can 202 00:09:18.440 --> 00:09:21.039 just break out instead of checking the other one hundred items. 203 00:09:21.440 --> 00:09:25.679 So if else switch for a while. Those are the 204 00:09:25.679 --> 00:09:26.960 core control tools. 205 00:09:26.679 --> 00:09:29.840 There really are. Mastering those lets you build the actual 206 00:09:29.919 --> 00:09:31.200 logic into your mod. 207 00:09:31.519 --> 00:09:35.360 Now, we talked about variables for single pieces of info, 208 00:09:35.759 --> 00:09:37.679 but what if you have like a whole bunch of things, 209 00:09:37.759 --> 00:09:40.840 say all the players online or a list of block 210 00:09:40.919 --> 00:09:44.320 coordinates for a structure, Making a separate variable for each 211 00:09:44.440 --> 00:09:46.919 seems inefficient, Totally inefficient. 212 00:09:47.120 --> 00:09:49.799 That's where arrays save the day. An array is a 213 00:09:49.840 --> 00:09:52.159 special kind of variable that holds a collection of items 214 00:09:52.200 --> 00:09:54.720 a list, basically kind of but with a key restriction. 215 00:09:55.039 --> 00:09:57.399 All items in a single array must be the same type. 216 00:09:57.440 --> 00:09:59.159 So you can have an array of vents or an 217 00:09:59.240 --> 00:10:02.519 array of string, but not a mix in one standard array. 218 00:10:02.639 --> 00:10:04.639 So an inter ray could hold all the y coordinates 219 00:10:04.639 --> 00:10:05.799 for a tower exactly. 220 00:10:05.879 --> 00:10:09.000 You create an array and specify its size upfront, like 221 00:10:09.080 --> 00:10:11.639 in chords equals new Inn fifty, it creates an array 222 00:10:11.639 --> 00:10:15.039 that can hold exactly fifty integers fixed size. Huh yep. 223 00:10:15.279 --> 00:10:18.519 That's a key characteristic of basic arrays. Each slot in 224 00:10:18.559 --> 00:10:21.039 the array is called an element, and you access them 225 00:10:21.120 --> 00:10:22.080 using an index. 226 00:10:21.840 --> 00:10:24.600 Number, and the index starts at zero. 227 00:10:24.720 --> 00:10:27.200 Always zero in Java. So the first element is an 228 00:10:27.240 --> 00:10:30.279 index zero, the second at index one up to index 229 00:10:30.360 --> 00:10:33.039 forty nine. In our fifty element array that. 230 00:10:32.919 --> 00:10:36.399 Reindeer names example in the guide really drove that fixedisz 231 00:10:36.480 --> 00:10:39.399 point home made an array for eight reindeers. 232 00:10:38.919 --> 00:10:41.639 And then poor Rudolph couldn't fit because the array was 233 00:10:41.639 --> 00:10:42.960 full there was no index eight. 234 00:10:43.080 --> 00:10:44.840 Right. How do you know how big an array is 235 00:10:44.879 --> 00:10:45.519 once you have it. 236 00:10:45.799 --> 00:10:49.039 Arrays have a handy length property, so ycords dot length 237 00:10:49.039 --> 00:10:50.120 would give you fifty. 238 00:10:50.360 --> 00:10:52.279 And what happens if you mess up and try to 239 00:10:52.320 --> 00:10:55.799 access say index fifty in that fifty element array. 240 00:10:55.919 --> 00:10:59.200 Boom, Well not quite boom, but your program will likely 241 00:10:59.240 --> 00:11:01.120 stop and throw an array index out of bounds. 242 00:11:01.159 --> 00:11:03.559 Exception an exception like an error. 243 00:11:03.399 --> 00:11:05.360 Yeah it's job as a way of saying you tried 244 00:11:05.360 --> 00:11:07.480 to access a part of the array that doesn't exist. 245 00:11:08.120 --> 00:11:11.279 The guide points out the specific exception usually means there's 246 00:11:11.320 --> 00:11:12.360 a flaw in your. 247 00:11:12.279 --> 00:11:15.080 Code logic something you need to fix. In the code itself, 248 00:11:15.240 --> 00:11:16.679 not just handle during runtime. 249 00:11:17.039 --> 00:11:19.879 Generally, yes, you should fix your loop or your index 250 00:11:19.919 --> 00:11:22.120 calculations so it doesn't try to go out of bounds. 251 00:11:22.919 --> 00:11:26.039 Arrays are fundamental, but the guide also briefly mentions other 252 00:11:26.080 --> 00:11:29.480 collection types, things like a ray list. It's more flexible, 253 00:11:29.519 --> 00:11:31.519 like a list that can grow or shrink as needed, 254 00:11:32.000 --> 00:11:36.320 much more convenient than fixed size arrays sometimes, and hash map, 255 00:11:36.559 --> 00:11:39.279 which is great for storing key value pair. 256 00:11:39.320 --> 00:11:41.120 KEYWTE like looking up a word in a dictionary. 257 00:11:41.240 --> 00:11:45.080 Exactly, you store something using a unique key like a 258 00:11:45.120 --> 00:11:48.279 player's name, a string and associate it with a value 259 00:11:48.440 --> 00:11:51.120 like their score an end. Then you can quickly retrieve 260 00:11:51.120 --> 00:11:54.200 the value just by knowing the key. Very useful structure. 261 00:11:54.279 --> 00:11:57.120 Okay, arrays and collections for handling groups of data. Now 262 00:11:57.360 --> 00:11:59.600 let's just step back a bit. The guide talks about 263 00:11:59.600 --> 00:12:03.200 a really big concept, object oriented programming. 264 00:12:02.960 --> 00:12:06.480 Op ah yes, oh ohp. It's a whole way of 265 00:12:06.480 --> 00:12:09.919 thinking about structuring your programs, and it's fundamental to Java 266 00:12:10.159 --> 00:12:13.799 and by extension, to Minecraft modding with things like spigot. 267 00:12:14.120 --> 00:12:17.360 So what does object oriented actually mean in this context? 268 00:12:17.519 --> 00:12:20.440 It means you design your program around objects. Think of 269 00:12:20.519 --> 00:12:24.639 objects as representations of well things. They could be real 270 00:12:24.679 --> 00:12:27.960 world things like a player, a wolf, a block, or 271 00:12:28.000 --> 00:12:30.679 more abstract things like a game rule or a server event. 272 00:12:30.799 --> 00:12:32.960 And what makes something an object? In code? 273 00:12:33.159 --> 00:12:35.840 Two main things to find an object. First, it has 274 00:12:35.960 --> 00:12:39.879 data associated with it, attributes or properties think variables, but 275 00:12:39.960 --> 00:12:43.480 belonging to that object. Second, it has behavior things that 276 00:12:43.559 --> 00:12:45.279 can do. These are called methods. 277 00:12:45.559 --> 00:12:47.679 Okay, So back to that zombie idea earlier. 278 00:12:47.720 --> 00:12:51.039 Perfect a zombie object would have attributes like health, maybe 279 00:12:51.120 --> 00:12:54.320 an int, location, maybe a location object is baby, a 280 00:12:54.320 --> 00:12:58.519 true false, a boolean that's the data right, and its behavior. 281 00:12:58.639 --> 00:13:02.000 It's methods would be things like attack player, target, move 282 00:13:02.120 --> 00:13:05.679 towards location, destination, take damage into mounts. 283 00:13:05.679 --> 00:13:08.759 So an object bundles is data and its actions. 284 00:13:08.360 --> 00:13:11.639 Together exactly the guide use a virus example, I think 285 00:13:11.639 --> 00:13:14.639 with attributes like identify an author, same principle, and a 286 00:13:14.720 --> 00:13:17.559 key part of OKP is controlling access to that data. 287 00:13:17.600 --> 00:13:18.840 The public and private stuff. 288 00:13:19.039 --> 00:13:23.120 Yes, you can mark attributes and methods as public meaning 289 00:13:23.200 --> 00:13:26.000 any part of your code can access them directly, or 290 00:13:26.080 --> 00:13:30.080 private meaning only the code inside that same object's class 291 00:13:30.080 --> 00:13:31.000 can access them. 292 00:13:31.039 --> 00:13:32.320 Why make things private? 293 00:13:32.679 --> 00:13:37.519 It's about encapsulation, protecting the object's internal state. Usually you 294 00:13:37.639 --> 00:13:41.679 keep the data health, etc. Private and provide public methods 295 00:13:41.919 --> 00:13:45.080 get health, set health to interact with it in a 296 00:13:45.120 --> 00:13:48.320 controlled way. It makes your code more robust and easier 297 00:13:48.360 --> 00:13:49.440 to manage. 298 00:13:49.039 --> 00:13:50.840 And methods can give back results you. 299 00:13:50.799 --> 00:13:54.039 Said yep using the return keyword. A method like get 300 00:13:54.039 --> 00:13:57.519 health would return the current value of the private health variable. 301 00:13:57.679 --> 00:14:01.120 A method that just performs an action like attack might 302 00:14:01.159 --> 00:14:03.519 not return anything. Its return type would be void. 303 00:14:03.639 --> 00:14:07.240 Okay, Then there were static methods. Those felt a bit different. 304 00:14:07.360 --> 00:14:09.600 They are a bit different. Remember, the class is the blueprint, 305 00:14:09.600 --> 00:14:11.759 and objects are the things made from the blueprint. Right, 306 00:14:11.879 --> 00:14:15.440 Normal methods belong to the objects. Static methods belong to 307 00:14:15.480 --> 00:14:18.440 the class itself, the blueprint. You don't need a specific 308 00:14:18.480 --> 00:14:20.120 object instance to use them. 309 00:14:20.320 --> 00:14:23.679 Like that integer dot parsing example, converting text to a. 310 00:14:23.720 --> 00:14:27.080 Number exactly, you don't need an integer object. You just 311 00:14:27.120 --> 00:14:31.159 call the method directly on the integer class integer parcent one, 312 00:14:31.200 --> 00:14:34.519 two three. They're often used for utility functions that don't 313 00:14:34.519 --> 00:14:37.000 depend on the state of a particular object. 314 00:14:36.679 --> 00:14:39.120 And making a new object, like a new zombie in 315 00:14:39.159 --> 00:14:41.639 the game that uses the new keyword. 316 00:14:41.320 --> 00:14:46.600 Correct zombie, My zombie equals new zombie When you use 317 00:14:46.679 --> 00:14:50.399 new a special method called a constructor gets called. 318 00:14:50.200 --> 00:14:52.159 Automatically a constructor. 319 00:14:52.559 --> 00:14:54.399 Yeah, it's a method with the same name as the 320 00:14:54.440 --> 00:14:58.039 class zombie, and its job is to initialize the new object, 321 00:14:58.120 --> 00:15:01.519 set up its initial state, give its attributes starting values. 322 00:15:01.799 --> 00:15:05.279 Cool. The guide also covered inheritance using extends. 323 00:15:05.279 --> 00:15:08.279 That sounds important, Oh, it's huge In Java and Minecraft. 324 00:15:08.480 --> 00:15:10.840 Inheritance is how you create classes that are based on 325 00:15:10.919 --> 00:15:13.320 other classes. You make a new class, the subclass or 326 00:15:13.399 --> 00:15:16.559 child that automatically gets all the non private attributes and 327 00:15:16.600 --> 00:15:18.000 methods from an existing class. 328 00:15:18.320 --> 00:15:21.200 The superclass reparent like a family tree for code. 329 00:15:20.960 --> 00:15:23.039 Kind of. So in Minecraft you might have a monster 330 00:15:23.080 --> 00:15:27.279 class that extends living entity, which extends entity. This means 331 00:15:27.320 --> 00:15:30.279 your monster automatically knows how to do everything an entity 332 00:15:30.360 --> 00:15:33.000 can like exist in the world at a location, and 333 00:15:33.080 --> 00:15:36.360 everything a living entity can like have health, take damage, 334 00:15:36.519 --> 00:15:38.919 plus any specific monster things you add, so you. 335 00:15:38.840 --> 00:15:41.200 Don't have to rewrite all that basic entity stuff every 336 00:15:41.200 --> 00:15:42.080 time exactly. 337 00:15:42.159 --> 00:15:45.799 It promotes code reuse and creates a logical hierarchy. Java 338 00:15:45.879 --> 00:15:49.399 itself has a base object class that everything ultimately inherits from. 339 00:15:49.519 --> 00:15:53.120 Okay, that op structure makes sense, but what happens when 340 00:15:53.120 --> 00:15:56.080 things just go wrong while the program is running, not 341 00:15:56.159 --> 00:16:00.399 a typo that net Beans catches, but like unexpect. 342 00:16:00.240 --> 00:16:03.320 Situations right run time problems, that's where exceptions come in. 343 00:16:03.759 --> 00:16:08.200 The guide described them as exceptional circumstances. The program hits 344 00:16:08.200 --> 00:16:11.720 a situation it wasn't necessarily designed to handle smoothly at 345 00:16:11.720 --> 00:16:13.039 that exact point, like. 346 00:16:12.960 --> 00:16:15.159 The user typing text when you expected a number. 347 00:16:15.320 --> 00:16:17.919 That's the classic example the new calculator, and the guide 348 00:16:17.960 --> 00:16:21.159 showed this perfectly. If your code tries to use integer 349 00:16:21.360 --> 00:16:24.720 dot parsin on the text hello, that's going to cause 350 00:16:24.720 --> 00:16:28.720 a problem. It would crash unless you handle the exception. 351 00:16:29.360 --> 00:16:32.759 Java lets you anticipate these problems using a tricatch block. 352 00:16:33.080 --> 00:16:33.759 How does that work? 353 00:16:33.919 --> 00:16:37.039 You put the code that might cause an exception, the 354 00:16:37.159 --> 00:16:41.320 risky code like integer dot parse end user input inside 355 00:16:41.360 --> 00:16:44.480 a tryblock. Immediately after it, you put a catch block. 356 00:16:44.600 --> 00:16:47.440 The catch block specifies the type of exception it's designed 357 00:16:47.440 --> 00:16:49.440 to handle, like number format exception. 358 00:16:49.639 --> 00:16:52.399 So if that specific error happens inside. 359 00:16:52.039 --> 00:16:55.399 Try, the program immediately jumps to the catch block for 360 00:16:55.480 --> 00:16:58.519 number format exception and runs the code inside that block 361 00:16:58.600 --> 00:17:01.879 instead of crashing. Do you Calculator example, use this to 362 00:17:01.919 --> 00:17:04.559 print a nice message like, Hey, that wasn't a number 363 00:17:04.759 --> 00:17:07.400 instead of just dying, that's much better. Yeah. 364 00:17:07.599 --> 00:17:10.599 The guide also mentioned other exceptions like that array index 365 00:17:10.640 --> 00:17:13.519 out of bounds exception again and null pointer exception. 366 00:17:13.720 --> 00:17:15.839 Yeah. Null pointer exception happens when you try to use 367 00:17:15.880 --> 00:17:18.440 a variable that hasn't been initialized to point to an 368 00:17:18.440 --> 00:17:21.720 actual objecto null pointing to nothing. 369 00:17:21.440 --> 00:17:23.359 And the guide said you shouldn't always try to catch those. 370 00:17:23.599 --> 00:17:26.599 It made the point that exceptions like array index outbounds 371 00:17:26.680 --> 00:17:30.400 or null pointer often signal a fundamental logic error in 372 00:17:30.440 --> 00:17:34.160 your code. While you could technically catch them, it's usually 373 00:17:34.200 --> 00:17:37.799 better practice to fix the underlying code flaw that's causing them, 374 00:17:38.200 --> 00:17:40.480 rather than trying to patch over it with a catch block. 375 00:17:41.039 --> 00:17:43.480 Prevent the error rather than just reacting to it. 376 00:17:43.680 --> 00:17:46.559 Got it, fix the bug. Okay, we've chewed through a 377 00:17:46.559 --> 00:17:49.759 lot of core Java there. The guide also glanced at 378 00:17:49.759 --> 00:17:52.160 a couple of slightly more advanced topics. 379 00:17:51.960 --> 00:17:55.200 Just briefly. One was threads. Threads are a way to 380 00:17:55.240 --> 00:17:58.119 make your program do multiple things seemingly at the same time, 381 00:17:58.480 --> 00:18:02.759 like multitasking. Much The prime Finder example showed this one 382 00:18:02.799 --> 00:18:05.119 part of the code. One thread could be doing heavy 383 00:18:05.160 --> 00:18:09.440 calculations while another thread updates the user interface or progress bar, 384 00:18:09.640 --> 00:18:11.599 keeping things responsive. 385 00:18:11.319 --> 00:18:13.920 Useful for long tasks in a mod maybe could be. 386 00:18:14.319 --> 00:18:17.519 And the other thing was file io input output, reading 387 00:18:17.559 --> 00:18:21.400 and writing files exactly using Java's built in libraries to 388 00:18:21.480 --> 00:18:25.079 read data from files like loading mod settings, or write 389 00:18:25.160 --> 00:18:28.920 data to files like saving player progress or configuration. The 390 00:18:28.960 --> 00:18:32.960 configurat example showed writing simple key value pairs like username 391 00:18:33.000 --> 00:18:36.119 max to a dot properties file. It involves concepts like 392 00:18:36.200 --> 00:18:39.599 data streams and remembering to close the file connection when 393 00:18:39.640 --> 00:18:40.119 you're done. 394 00:18:40.200 --> 00:18:44.920 Okay, wow, that's a lot of Java. Now the payoff. 395 00:18:45.559 --> 00:18:49.839 How does all this variables, loops, objects, exceptions actually let 396 00:18:49.880 --> 00:18:53.279 you make a Minecraft mod using something like spiggot, which 397 00:18:53.319 --> 00:18:54.480 the guide mentioned right. 398 00:18:54.559 --> 00:18:57.160 This is where it connects. Spigot is a popular modified 399 00:18:57.200 --> 00:18:59.839 Minecraft server software that provides an API, a set of 400 00:18:59.839 --> 00:19:03.000 two tools and interfaces for mod developers. Your mod is 401 00:19:03.079 --> 00:19:05.640