Core Java Programming Language (JSE) : Chapter V - Arrays

Core Java Programming Language (JSE) : Chapter V - Arrays

• 1.
  Java Programming LanguageSE – 6 Module 5 : Arrays
• 2.
  www.webstackacademy.com Objectives ● Declare andcreate arrays of primitive, class, or array types ● Explain why elements of an array are initialized ● Explain how to initialize the elements of an array ● Determine the number of elements in an array ● Create a multidimensional array ● Write code to copy array values from one array to another
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  www.webstackacademy.com Creating Arrays Use thenew keyword to create an array object. For example, a primitive (char) array: public char[] createArray() { char[] s; s = new char[26]; for ( int i=0; i<26; i++ ) { s[i] = (char) (’A’ + i); } return s; }
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  www.webstackacademy.com Creating an Arrayof Character Primitives
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  www.webstackacademy.com Creating Reference Arrays Anotherexample, an object array: public Point[] createArray() { Point[] p; p = new Point[10]; for ( int i=0; i<10; i++ ) { p[i] = new Point(i, i+1); } return p; }
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  www.webstackacademy.com Initializing Arrays ● Initializean array element. ● Create an array with initial values. String[] names; names = new String[3]; names[0] = "Georgianna"; names[1] = "Jen"; names[2] = "Simon";
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  www.webstackacademy.com Multidimensional Arrays ● Arraysof arrays: int[][] twoDim = new int[4][]; twoDim[0] = new int[5]; twoDim[1] = new int[5]; int[][] twoDim = new int[][4]; // illegal ● Array of four arrays of five integers each: int[][] twoDim = new int[4][5];
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  www.webstackacademy.com Array Bounds All arraysubscripts begin at 0: public void printElements(int[] list) { for (int i = 0; i < list.length; i++) { System.out.println(list[i]); } }
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  www.webstackacademy.com Using the Enhanced forLoop ● Java 2 Platform, Standard Edition (J2SETM) version 5.0 introduced an enhanced for loop for iterating over arrays: public void printElements(int[] list) { for ( int element : list ) { System.out.println(element); } }
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  www.webstackacademy.com Array Resizing ● Youcannot resize an array. ● You can use the same reference variable to refer to an entirely new array, such as: int[] myArray = new int[6]; myArray = new int[10];
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  www.webstackacademy.com Copying Arrays The System.arraycopy()method to copy arrays is: //original array int[] myArray = { 1, 2, 3, 4, 5, 6 }; // new larger array int[] hold = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 }; // copy all of the myArray array to the hold // array, starting with the 0th index System.arraycopy(myArray, 0, hold, 0, myArray.length);
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