Arrays in Object-Oriented Programming 2 PDF

CHAPTER 1 ARRAYS IT-PF02 – Object-Oriented Programming 2 LEARNING OBJECTIVES At the end of this chapter, the students are able to:  Declaring arrays;  Initializing an array;  Use variable subscripts with an array;  Declaring and using arrays of objects; and  Searc...

CHAPTER 1 ARRAYS IT-PF02 – Object-Oriented Programming 2 LEARNING OBJECTIVES At the end of this chapter, the students are able to:  Declaring arrays;  Initializing an array;  Use variable subscripts with an array;  Declaring and using arrays of objects; and  Search an array and use parallel arrays. ARRAYS Arrays is a collection of multiple values in a single variable with the same data type they are governed by using an index. For example: String[] student_names; To insert values in an array, we put an equal sign (=) followed by curly brace {}. Inside the curly brace, each value is listed and separated by a comma (,). If the values are string literals, we enclosed them by a double quote (“”). Each individual value of an array is called an element. For example; (DECLARE WITH VALUES) String[] student_names = {“Anna”, “Lorna”, “Fe”} On the other hand, we can also declare an array of integers. For example: int[] myNum = {5, 10, 15, 20}; Alternatively, we can also declare an array with no initial values but reserves a memory space for the elements the array will hold. It is through the way we create an object. (DECLARE WITHOUT VALUES) For example: int[] myNum = new int ;  ARRAYS (CONT..) The new keyword instantiates a new array. A subscript is an integer contained within square brackets that specifies one of an array’s elements. In Java, any array’s elements are numbered beginning with 0, so you can legally use any subscript from 0 through 3 when working with an array that has 4 elements. In other words, the first myNum array element is myNum and the last myNum element is myNum Valu e Inde x To declare individual values to the array we just declared using this method, we can simply use the way how we place values on our variables. For example:  ARRAYS (CONT..) If you use a subscript that is too small (that is, negative) or too large for an array, the subscript is out of bounds and an error message is generated. ARRAYS (CONT..) If you use a subscript that is too small (that is, negative) or too large for an array, the subscript is out of bounds and an error message is generated. ARRAYS (CONT..) To initialize an array, you use an initialization list of values separated by commas and enclosed within curly braces. Providing values for all the elements in an array also is called populating the array. For example, if you want to create an array named myNum and store the five numbers within the array, you can declare the array as follows: ARRAY COMPUTE CHANGE AN ARRAY ELEMENT To change the value of a specific element, refer to the index number: ARRAY LENGTH Array length is to determine the size of an array in your code. To find out how many elements an array has, use the length keyword. ARRAY LOOP USING FOR LOOP You can loop through the array elements with the for loop and use the length property to specify how many times the loop should run. ARRAY LOOP USING FOR-EACH LOOP There is also a "for-each" loop, which is used exclusively to loop through elements in arrays: MULTI-DIMENSIONAL ARRAY A multidimensional array is an array of arrays. Multidimensional arrays are useful when you want to store data as a tabular form, like a table with rows and columns. To create a two-dimensional array, add each array within its own set of curly braces: myNumbers is now an array with two arrays as its elements. int[][] myNumbers = new int[] creates a jagged array, where each row can have a different number of columns. // Initialize each row separately with its respective column size myNumbers = new int; // Row 0 has 3 columns myNumbers = new int; // Row 1 has 3 columns MULTI-DIMENSIONAL ARRAY (CONT..) LOOP THROUGH 2-DIMENSIONAL ARRAY (2D ARRAY) LOOP THROUGH 3-DIMENSIONAL ARRAY (3D ARRAY)