Java Tutorial #15.1 / 15.2 — Introduction to and using arrays

Topics Discussed: Arrays, subscripts, iterating through arrays

Source Code Below

 

15.2

Topics discussed: Same as above

Source Code for Lesson 15-1 / 15-2

import java.util.Scanner;
class Jtutorial1 {
    public static void main(String args[]){
    Scanner input = new Scanner(System.in);
 
    //int i= 5;    i(5);
    //int anArray[] = new int[5];
 
    //anArray[ | | | | ];
    //anArray[0|0|0|0|0]; // initialize to 0
    //anArray[0|1|2|3|4]; // index. 0th, 1st, 2nd, 3rd, 4th
    //anArray[1|2|3|4|5]; // 
    //anArray[ | |3| | ]; // 3
 
    System.out.println("\nHow many items would you like to enter? : ");
    int x = input.nextInt(); //3
 
    int itemArray[] = new int[x];
    double itemCost[] = new double[x];
 
    for (int i = 0; i < itemArray.length; i++){ // initializing arrays to 0
        itemArray[i] = 0; // [i] Subscript.  
        itemCost[i] = 0;  // anArray[2] i=2  anArray[i]
        //itemArray / itemCost[ 0 | 0 | 0 ]  // 0, 1, 2
    }
 
    for(int i=0; i< itemArray.length; i++){
        System.out.println("\nEnter the unique, item ID: ");
        itemArray[i] = input.nextInt();
 
        System.out.println("\nEnter the cost for that item: ");
        itemCost[i] = input.nextDouble();
    }
    System.out.println();
    System.out.println();
    System.out.println("Price list: ");
    for(int i=0; i < itemArray.length; i++){
        System.out.println("The value of i is: " + i + "  Item Number: " + (itemArray[i]) + " = $" + itemCost[i]);
    }
 
 
 
    }//end main
}//end class
 
 
 
//Create an array, to enter user entered numbers. 
 
//10
 
//a, a, a, a, c, c, c, d, f, g

Homework:

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    Create an array of characters that correspond to SOMETHING meaningful to you and output that many characters.
     
    Example, my name
     
    'Damien'
     
    User enters 3
     
    program outputs 'Dam'

Arrays
Arrays are the most basic multi-variable container made available in java. The syntax is pretty simple, but the implementation can be confusing if you don’t have a programming background. The basic specifications of an array is that it’s a basic, 0-indexed, template’d, data structure that can be created with either explicit values or in an empty state.

int anArray[] = new int[7]; // Creates an array that can hold 7 ints.
for(int i=0; i< anArray.length(); i++){
    anArray[i] = i; // sets the array equal to it's index based off the iteration in a loop.
}

Arrays can be iterated through easily with loops, especially by for loops.

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The Subscript
The subscript is the way that we access a certain part of an array. anArray[0] would refer to the ‘first’ (remember, 0-indexed) location in the array. Therefore the subscript in this case would be 0. Changing the subscript from within a loop is fairly common practice in Object oriented programming.