Array Basics
/**
* ARRAYS in JAVA
* --------------
* Arrays in Java have fixed size.
* They can store either primitives or objects (wrappers unboxing).
*
* Arrays are low-level structures, very fast.
* Arrays are less flexible than ArrayList.
*
* Arrays are not part of the Collections framework.
* Arrayts are part of the java.util package.
*
* Collections:
* - Arrays.copyOf() creates a new array, not just a new reference.
*/
package com.minte9.collections.arrays;
import java.util.Arrays;
public class ArrayBasics {
public static void main(String[] args ) {
// Create and populate
String[] arr = new String[3];
arr[0] = "a";
arr[1] = "b";
arr[2] = "c";
// Get element (by index)
String first = arr[0];
System.out.println("First " + first); // a
// Set element
arr[1] = "x";
System.out.println("Changed " + arr[1]); // x
// Iterate using enhanced for loop
for (String s : arr) {
System.out.println(s); // a x c
}
// Size
int size = arr.length;
System.out.println("Length " + size); // 3
// Object unboxing
int[] nums = {1, 2, 3, 0};
nums[2] = 4;
nums[3] = Integer.parseInt("4");
System.out.println(nums[3]); // 4
// Copy arrays safely
int[] copy = Arrays.copyOf(nums, nums.length);
// Chaning the copy does not affect the original
copy[0] = 100;
System.out.println("Original: " + nums[0]); // 1
// Changing the original does not affect the copy
nums[0] = 999;
System.out.println("Copy: " + copy[0]); // 100
// Array intialization with literals
String[] chars = {"a", "b", "c", "d"};
System.out.println(chars[0]); // a
int[][] matrix = {
{1, 2, 3},
{4, 5, 6},
{7, 8, 9},
};
System.out.println(matrix[1][2]); // 6
}
}
Array Examples
/**
* ARRAYS EXAMPLES
* ---------------
*/
package com.minte9.collections.arrays;
public class ArrayExamples {
public static void main(String[] args) {
// GRADES - Fixed number of grades - exactly 5
// -------------------------------------------
int[] grades = new int[5];
grades[0] = 85;
grades[1] = 90;
grades[2] = 78;
grades[3] = 92;
grades[4] = 88;
System.out.println(
"Exam grades: " + grades.length // Exam grades: 5
);
for (int g : grades) {
System.out.print(g + " "); // 85 90 78 92 88
}
// WEEK DAYS - Fixed numer of week days
// ------------------------------------
String days[] = {"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"};
System.out.println(
"Week days: " + days.length // Week days: 7
);
for (String d : days) {
System.out.print(d + " "); // Mon Tue Wed Thu Fri Sat Sun
}
}
}
