public class ArrayBasics
1: import java.util.Scanner;
3: /**
4: * Some simple array manipulations.
5: *
6: * @author Mark Young (A00000000)
7: */
8: public class ArrayBasics {
10: /**
11: * Run this program.
12: *
13: * @param args command lines arguments (ignored)
14: */
15: public static void main(String[] args) {
16: // introduce self
17: System.out.println("\n"
18: + "Just doing some array things."
19: + "Look at the code and compare it to the output.\n");
21: // an array type is just another data type
22: int anIntVar; // type int
23: int[] aBunchOfIntVars; // type int[]
25: // you can make an array out of /any/ data type
26: double[] aBunchOfDoubleVars; // doubles
27: String[] aBunchOfStringVars; // Strings
28: Scanner[] aBunchOfScannerVars; // Scanners
29: int[][] aBunchOfIntArrayVars; // int[]s (!)
31: // like other variables, array vars need to be given values
32: // like Scanners, use the word "new" to make the value
33: Scanner kbd = new Scanner(System.in);
34: // unlike Scanners, it's []s after the data type, not ()s
35: double[] someNumbers = new double[20];
36: String[] someWords = new String[1000];
38: // size of the array can be a variable
39: System.out.print("How many lines will you be entering? ");
40: int numLines = kbd.nextInt(); kbd.nextLine();
41: String[] theLines = new String[numLines];
43: // Array usually used as a group
44: // (doing the same thing to each element)
45: for (int i = 0; i < someNumbers.length; i++) {
46: // pick out array elements using []
47: someNumbers[i] = Math.sqrt(i);
48: // number inside the brackets is called an index
49: }
50: // but you can use array elements as individual variables
51: System.out.println("someNumbers[10] == " + someNumbers[10]);
53: // read some lines
54: System.out.println("\n"
55: + "Let's enter those lines, now:");
56: for (int i = 0; i < numLines; i++) {
57: theLines[i] = kbd.nextLine(); // no need to tidy up
58: }
60: // print the lines (reversed)
61: System.out.println("\n"
62: + "Here are the lines you entered, in reverse order:");
63: for (int i = numLines - 1; i >= 0; i--) {
64: System.out.println("\t\"" + theLines[i] + "\"");
65: }
66: System.out.print("\n---Press Enter to continue---");
67: kbd.nextLine();
69: // print the square roots
70: System.out.println("\n"
71: + "And here are the square roots I calculated earlier:");
72: for (int i = 0; i < someNumbers.length; i++) {
73: System.out.println("\tsqrt(" + i + ") is " + someNumbers[i]);
74: }
75: System.out.println();
76: }
78: }