Chapter7 Notes

Chapter7 Notes - 1 Arrays Arrays are objects that help us...

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Unformatted text preview: 1 Arrays Arrays are objects that help us organize large amounts of information Chapter 7 focuses on array declaration and use bounds checking and capacity arrays that store object references variable length parameter lists multidimensional arrays Outline Arrays Declaring and Using Arrays Arrays of Objects Command Line Arguments Variable Length Parameter Lists Two-Dimensional Arrays 2 7.1 Arrays An array is an ordered list of values 0 1 2 3 4 5 6 7 8 9 79 87 94 82 67 98 87 81 74 91 An array of size N is indexed from zero to N-1 scores The entire array has a single name Each value has a numeric index This array holds 10 values that are indexed from 0 to 9 7.1 Arrays A particular value in an array is referenced using the array name followed by the index in brackets For example, the expression scores[2] refers to the value 94 (the 3rd value in the array) That expression represents a place to store a single integer and can be used wherever an integer variable can be used 3 7.1 Arrays For example, an array element can be assigned a value, printed, or used in a calculation scores[2] = 89; scores[first] = scores[first] + 2; mean = (scores[0] + scores[1])/2; System.out.println ("Top = " + scores[5]); 7.1 Arrays The values held in an array are called array elements An array stores multiple values of the same type the element type The element type can be a primitive type or an object reference Therefore, we can create an array of integers, an array of characters, an array of String objects, an array of Coin objects, etc. In Java, the array itself is an object that must be instantiated 4 7.1 Arrays Another way to depict the scores array scores 79 87 94 82 67 98 87 81 74 91 Outline Arrays Declaring and Using Arrays Arrays of Objects Command Line Arguments Variable Length Parameter Lists Two-Dimensional Arrays 5 7.2 Declaring Arrays The scores array could be declared as follows int scores = new int[10]; The type of the variable scores is int (an array of integers) Note that the array type does not specify its size, but each object of that type has a specific size The reference variable scores is set to a new array object that can hold 10 integers 7.2 Declaring Arrays Some other examples of array declarations float prices = new float[500]; boolean flags; flags = new boolean[20]; char codes = new char[1750]; 6 7.2 Using Arrays The iterator version of the for loop can be used when processing array elements for (int score : scores) System.out.println (score); This is only appropriate when processing all array elements from top (lowest index) to bottom (highest index) 7.2 BasicArray.java //******************************************************************** // BasicArray.java Java Foundations // // Demonstrates basic array declaration and use....
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Chapter7 Notes - 1 Arrays Arrays are objects that help us...

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