Revision of IntroJavaArrays

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introjavaarrays.md

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128	128		## Summary
129	129
130	130		Arrays in Java allow you to store multiple values of the same type under a single variable name. They have a fixed size, use zero-based indexing, and provide a simple way to manage collections of data. As you progress in your programming journey, you'll find arrays to be an essential tool for solving many types of problems efficiently.
131		-
132		-	In your next programming exercises, try creating and manipulating arrays to store collections of related data, and experiment with different ways to process the elements they contain.

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introjavaarrays.md(fájl létrehozva)

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1	+	# Java Arrays: An Introduction for Beginners
2	+
3	+	Arrays are one of the most fundamental data structures in Java programming. They allow you to store multiple values of the same type under a single variable name, making your code more organized and efficient. This introduction will help you understand what arrays are, how they work, and how to use them effectively in your Java programs.
4	+
5	+	## What Is an Array?
6	+
7	+	An array is a container that holds a fixed number of values of a single type. Think of an array as a row of boxes, where each box can store one item. All items in an array must be of the same data type - whether that's integers, floating-point numbers, characters, or even objects.
8	+
9	+	## Why Use Arrays?
10	+
11	+	Imagine you need to store 100 student scores. Without arrays, you would need to create 100 separate variables! With arrays, you can simply create one variable that holds all 100 scores, making your code cleaner and easier to manage.
12	+
13	+	## Declaring Arrays in Java
14	+
15	+	There are several ways to declare arrays in Java:
16	+
17	+	```java
18	+	// Declaration only
19	+	int[] numbers;
20	+
21	+	// Declaration with size
22	+	int[] scores = new int[10]; // Creates an array that can hold 10 integers
23	+
24	+	// Declaration with initialization
25	+	String[] names = {"John", "Emma", "Michael", "Sophia"};
26	+	```
27	+
28	+	When you declare an array with a specific size but don't initialize values, Java automatically assigns default values (0 for numeric types, false for boolean, null for objects).
29	+
30	+	## Array Indexing
31	+
32	+	Each position in an array is identified by an index, which starts at 0 (not 1). This means:
33	+	- The first element is at index 0
34	+	- The second element is at index 1
35	+	- The last element is at index (length-1)
36	+
37	+	```java
38	+	int[] numbers = {10, 20, 30, 40, 50};
39	+	System.out.println(numbers[0]); // Outputs: 10
40	+	System.out.println(numbers[2]); // Outputs: 30
41	+	```
42	+
43	+	## Accessing and Modifying Array Elements
44	+
45	+	You can access array elements using square brackets with the index number:
46	+
47	+	```java
48	+	// Access element at index 2
49	+	int thirdNumber = numbers[2];
50	+
51	+	// Modify element at index 1
52	+	numbers[1] = 25;
53	+	```
54	+
55	+	## Array Length
56	+
57	+	Every Java array has a `length` property that tells you how many elements the array can hold:
58	+
59	+	```java
60	+	int[] scores = new int[10];
61	+	System.out.println(scores.length); // Outputs: 10
62	+	```
63	+
64	+	## Common Array Operations
65	+
66	+	### Iterating Through Arrays
67	+
68	+	The most common operation is to process each element in an array:
69	+
70	+	```java
71	+	// Using for loop
72	+	for (int i = 0; i < numbers.length; i++) {
73	+	System.out.println("Element at index " + i + ": " + numbers[i]);
74	+	}
75	+
76	+	// Using enhanced for loop (for-each)
77	+	for (int number : numbers) {
78	+	System.out.println(number);
79	+	}
80	+	```
81	+
82	+	### Finding the Sum of Array Elements
83	+
84	+	```java
85	+	int[] numbers = {5, 10, 15, 20, 25};
86	+	int sum = 0;
87	+
88	+	for (int number : numbers) {
89	+	sum += number;
90	+	}
91	+
92	+	System.out.println("Sum: " + sum); // Outputs: 75
93	+	```
94	+
95	+	### Finding the Largest Element
96	+
97	+	```java
98	+	int[] numbers = {12, 7, 19, 23, 8, 16};
99	+	int max = numbers[0]; // Assume first element is the largest
100	+
101	+	for (int i = 1; i < numbers.length; i++) {
102	+	if (numbers[i] > max) {
103	+	max = numbers[i];
104	+	}
105	+	}
106	+
107	+	System.out.println("Largest number: " + max); // Outputs: 23
108	+	```
109	+
110	+	## Common Mistakes and Pitfalls
111	+
112	+	1. Array Index Out of Bounds: Attempting to access an index that doesn't exist will throw an `ArrayIndexOutOfBoundsException`:
113	+
114	+	```java
115	+	int[] numbers = {1, 2, 3};
116	+	System.out.println(numbers[3]); // Error! Valid indices are 0, 1, and 2
117	+	```
118	+
119	+	2. Forgetting That Arrays Are Fixed-Size: Once created, an array's size cannot be changed. If you need a resizable collection, consider using `ArrayList`.
120	+
121	+	3. Not Initializing Arrays: Declared but uninitialized arrays are `null`:
122	+
123	+	```java
124	+	int[] numbers; // Declared but not initialized
125	+	numbers[0] = 10; // This will cause a NullPointerException
126	+	```
127	+
128	+	## Summary
129	+
130	+	Arrays in Java allow you to store multiple values of the same type under a single variable name. They have a fixed size, use zero-based indexing, and provide a simple way to manage collections of data. As you progress in your programming journey, you'll find arrays to be an essential tool for solving many types of problems efficiently.
131	+
132	+	In your next programming exercises, try creating and manipulating arrays to store collections of related data, and experiment with different ways to process the elements they contain.

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