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This resource covers the foundational concepts of arrays in Java, including creating and manipulating single and multi-dimensional arrays. It explains how to declare and initialize arrays for various data types such as strings, integers, and doubles. The tutorial includes examples of reading from files, computing averages, and using dynamic arrays with ArrayList. You will learn to work with both fixed-length and dynamic arrays, as well as practice exercises to enhance your understanding of array operations in Java programming.
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http://discern.uits.iu.edu:8790/S517/S517.html Web Programming Array Xiaozhong Liu
An Array of… (Strings, integers, doubles) A list of Object Information problem… Output Input Process An Object A Variable (String, int, Double)
Temperature File, 5 temperatures double [ ] temperatures = new double[5]; //Write to those variables (Array) 30.5 -15.3 0 60.35 18.12 temperatures [0] temperatures [1] temperatures [2] temperatures [3] temperatures [4]
Type Array name String Array String [ ] students = new String [25]; Array Declarations Variable value int Array int [ ] age = new int [100]; double double [ ] heights = new double [50];
int [ ] numbers = new int [50]; … //e.g.read from a file ‘Average numbers??? Average of numbers int sum = 0; double average; for (int index = 0; index<50; index++) { sum = sum + numbers [index]; } average = ????????
int [ ][ ] numbers = new int [2][3]; 2 – Dimensional Array
int [ ][ ] numbers = new int [3][5]; double average, sum = 0; 2 – Dimensional Array • for (int row= 0; row<3; row++) { • for (intcol = 0; col < 5; col++) { • sum = sum + numbers [row] [col]; • } • } • average = ?????????
int[ ] numbers = new int[20], squares = new int[20]; for (inti = 0; i < numbers.length; i++) { numbers[i] = i + 1; } //Compute squares??? //Average of squares??? Practice
double [ ] numbers = new double[5]; double [ ] numbers = {2.1, 43.1, 0, -0.3, 35.0}; You can use for loop How about dynamic array? Fix length array
double [ ] numbers = new double[5]; import java.util.ArrayList; ArrayListal = new ArrayList(); al.add("C"); al.add("A"); al.add("E"); al.add(1, "A2"); for (int i = 0; i < al.size(); i ++) { Stringitem = (String)al.get(i); System.out.println(item); } Dynamic array