CSE 131 Quiz 1 Makeup Solutions
Data Types and Expressions
28 Feb 2011
1. (60 points) Complete the following table by filling in the value and type of each
expression. Assume that variables i and x have been declared and initialized by the
statements shown below.
int i = 13; double x = 27.2
Expression
Value
Type
2 + 2.0
4.0
double
11/3
3
int
2*3 + “9” + (5 - 2)
“693”
String
x /2 == i
false
boolean
(x < 23) && (i < 7) || (i < x)
true
boolean
5 * 3 / 2 == 5 * (3 / 2)
false
boolean
2.0 * (++i )
28.0
double
2. (40 points) The following method is supposed to return the sum of the integers from m
through n (so, sumRange(2,4) should equal 2+3+4=9). It is based on the fact that
1+2+...+n = (1/2)n(n+1). Assume 0 < m  n.
public static int sumRange (int m, int n) {
return (n/2)*(n+1) - (m/2)*(m-1);
}
a. What are the input types for this method (i.e., what are the types of the formal
parameters)? (10 pts))
int
b. What value is returned by the method when it is called with arguments 3 and 5? (10
pts)
(5/2)*6 - (3/2)*2 = 12 - 2 = 10
c. Show how to re-write the return statement, so that the method always returns the
correct result. Your solution should use only integer arithmetic (no type conversions)
and should not use either iteration or recursion. Hint: the product of any two
consecutive integers is an even number.
return n*(n+1)/2 - m*(m-1)/2;