Arrays of ints in Java


import java.util.Scanner;

public class IntArray {

	/**
	 * The class illustrates arrays of integers in Java
	 * Author: Elena Machkasova
	 * For: CSci 2101
	 */
	public static void main(String[] args) {
		int [] simpleArray = {3, -1, 4};
		
		// this prints the address of the array, 
		// not the elements. You need a loop to print 
		// elements
		System.out.println(simpleArray);
		
		// a method that prints an array element by element
		// (see below)
		printIntArray(simpleArray);
		
		// the loop adds 1 to each element of simpleArray
		for (int i = 0; i < simpleArray.length; ++i) {
			simpleArray[i] = simpleArray[i] + 1; 
		}
		
		printIntArray(simpleArray);
		
		// creating an array whose size is given by a variable:
		
		// reading in the array size
		Scanner read = new Scanner(System.in);
		System.out.println("Please enter the array size:");
		int n = read.nextInt();
		
		// creating a new array:
		int [] arr = new int[n];
		
		// all elements are initialized to the default int value 0:
		printIntArray(arr);
		
		// setting elements to numbers from n to 1 (decreasing):
		for(int i = 0; i < arr.length; ++i) {
			arr[i] = n - i;
		}
		
		printIntArray(arr);

		System.out.println(sumArray(arr));
	}
	
	/**
	 * 
	 * The method prints its argument <code>arr</code>

	 * element by element on one line, separated by commas,
	 * with [ before the first element and ] after the last one 
	 *
	 */
	public static void printIntArray(int [] arr) {
		System.out.print("[");
		for (int i = 0; i < arr.length; ++i) {
			System.out.print(arr[i]);
			if (i != arr.length - 1)
				System.out.print(", ");
		}
		System.out.println("]");
	}
    /** 
	The method takes an array of integers and computes and
	returns its sum
     **/
    public static int sumArray(int [] arr) {
	int sum = 0;
	// enhanced 'for' loop, a.k.a. for-each loop
	// can be used when indices don't matter
	// and the array is not modified
	for (int item: arr) {
	    sum += item; // the same as: sum = sum + item;
	}
	return sum;
    }

}

CSci 2101 course web site.

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