<![CDATA[
CSE142 Program Example handout #21
Program file Histogram.java
---------------------------
// Stuart Reges
// 11/10/04
//
// This program reads an input file of test scores (integers) and displays a
// histogram of the score distribution.
import java.io.*;
public class Histogram {
public static final int MAX_SCORE = 101; // max possible score
public static void main(String[] args) {
System.out.println("This program reads a file of exam scores and");
System.out.println("displays the scores in a histogram.");
System.out.println();
// open file
Scanner console = new Scanner(System.in);
Scanner input = getInput(console);
// read file into count array
int[] count = new int[MAX_SCORE + 1];
while (input.hasNextInt())
count[input.nextInt()]++;
// use array to produce a histogram
for (int i = 0; i < count.length; i++)
if (count[i] != 0) {
System.out.print(i + ": ");
for (int j = 1; j <= count[i]; j++)
System.out.print("*");
System.out.println();
}
}
// prompts the user for a file name and reads the result using the
// console Scanner until the user gives a legal file name
public static Scanner getInput(Scanner console) {
Scanner result = null;
while (result == null) {
System.out.print("What is the name of the input file? ");
String name = console.nextLine();
try {
result = new Scanner(new File(name));
} catch (FileNotFoundException e) {
System.out.println("File not found. Please try again.");
}
}
System.out.println();
return result;
}
}
Histogram output
----------------
17: *
19: *
25: **
26: *
30: *
31: *
32: *
37: *
38: *
39: *
40: *
42: *
43: *
44: *
46: ****
47: **
48: ***
49: ****
50: **
51: *
52: *
53: ***
54: ***
55: *
56: ***
57: *
58: *******
59: **
60: ***
61: **
62: ******
63: ***
64: ***
65: **
66: ***
67: ****
68: *********
69: *****
70: **********
71: *****
72: ********
73: *************
74: ******
75: *****
76: ****
77: ********
78: ***
79: *********
80: ***********
81: **********
82: ********
83: ***************
84: *************
85: *******
86: ****************
87: *****************
88: ************
89: **********
90: *******
91: **********
92: ***
93: ***************
94: *****
95: *******************
96: *********
97: *********
98: **********
99: **********************
100: ******
101: **********
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