Transcript Chapter 4 Practice (cont.)

Chapter 4 Practice
cont.
Practice with nested loops
1. What will be the output of the following
program segment:
1. for (int i = 1; i <5; i++) {
for (int j = 1; j < 5; j++)
System.out.print (2*i+j + “ “);
System.out.println();
}
2. for (int i = 1; i <5; i++) {
for (int j = 0; j <= i; j++)
System.out.print (2*i+j + “ “);
System.out.println();
}
Practice with File input and output
1. Write code that does the following: opens
a file named MyName.txt, writes your
name to the file, then closes the file.
2. Write code that does the following: opens
a file named MyName.txt, reads the first
line from the file and displays it, then
closes the file.
3. A text file contains a sequence of integers,
each in a separate line. Write code that
reads this file and displays the sum of all
numbers in the file.
Practice with Random class
1. Write code to display a random number in the
interval [0, 1).
2. Write code to display a random number in the
interval [0, 100).
3. Write code to display a random number in the
interval [13, 19] (teenager)
4. Write code to display a random letter [A..Z]
5. Write code to display a string of 5 random
letters.
Sample Problems
1. The sum S(n) is defined as:
S(n) = 1 + ½ + 1/3 + … + 1/n.
Write a program that reads a number M from
keyboard, then displays the smallest value of n
so that S(n) >= M.
2. Write a program to calculate the square root of a
non-negative number n, using the while loop.
Compare the result with the Math.sqrt() method.
See instructions in class.