Scanner#hasNext()
is going to return a boolean value indicating whether or not
there is more input
and as long as the user has not entered end-of-file
indicator, hasNext() is going to return true
The end-of-file indicator is a system-dependent keystroke
combination
which the user enters to indicate that there’s no more data to input.
on UNIX/Linux/Mac OS X it's ctrl + d,,, On Windows it's ctrl + z
look at this simple example to see how to use it
// Fig. 5.9: LetterGrades.java
// LetterGrades class uses the switch statement to count letter grades.
import java.util.Scanner;
public class LetterGrades
{
public static void main(String[] args)
{
int total = 0; // sum of grades
int gradeCounter = 0; // number of grades entered
int aCount = 0; // count of A grades
int bCount = 0; // count of B grades
int cCount = 0; // count of C grades
int dCount = 0; // count of D grades
int fCount = 0; // count of F grades
Scanner input = new Scanner(System.in);
System.out.printf("%s%n%s%n %s%n %s%n",
"Enter the integer grades in the range 0–100.",
"Type the end-of-file indicator to terminate input:",
"On UNIX/Linux/Mac OS X type <Ctrl> d then press Enter",
"On Windows type <Ctrl> z then press Enter");
// loop until user enters the end-of-file indicator
while (input.hasNext())
{
int grade = input.nextInt(); // read grade
total += grade; // add grade to total
++gradeCounter; // increment number of grades
// increment appropriate letter-grade counter
switch (grade / 10)
{
case 9: // grade was between 90
case 10: // and 100, inclusive
++aCount;
break; // exits switch
case 8: // grade was between 80 and 89
++bCount;
break; // exits switch
case 7: // grade was between 70 and 79
++cCount;
break; // exits switch
case 6: // grade was between 60 and 69
++dCount;
break; // exits switch
default: // grade was less than 60
++fCount;
break; // optional; exits switch anyway
} // end switch
} // end while
// display grade report
System.out.printf("%nGrade Report:%n");
// if user entered at least one grade...
if (gradeCounter != 0)
{
// calculate average of all grades entered
double average = (double) total / gradeCounter;
// output summary of results
System.out.printf("Total of the %d grades entered is %d%n",
gradeCounter, total);
System.out.printf("Class average is %.2f%n", average);
System.out.printf("%n%s%n%s%d%n%s%d%n%s%d%n%s%d%n%s%d%n",
"Number of students who received each grade:",
"A: ", aCount, // display number of A grades
"B: ", bCount, // display number of B grades
"C: ", cCount, // display number of C grades
"D: ", dCount, // display number of D grades
"F: ", fCount); // display number of F grades
} // end if
else // no grades were entered, so output appropriate message
System.out.println("No grades were entered");
} // end main
} // end class LetterGrades
and the output will be something like this
Enter the integer grades in the range 0–100.
Type the end-of-file indicator to terminate input:
On UNIX/Linux/Mac OS X type <Ctrl> d then press Enter
On Windows type <Ctrl> z then press Enter
99
92
45
57
63
71
76
85
90
100
^Z
Grade Report:
Total of the 10 grades entered is 778
Class average is 77.80
Number of students who received each grade:
A: 4
B: 1
C: 2
D: 1
F: 2
Resources Learning Path: Professional Java Developer
and Java™ How To Program (Early Objects), Tenth Edition