APCS Java Unit 4 Practice Test - Arrays and Strings

Name:

Multiple Choice
Identify the choice that best completes the statement or answers the question.

Consider the following method:

public static int[] what(int[] A)
{
      int n = A.length;
      int[] temp = new int[n] ;
      for(int i=0; i<n; i++)
      {
            temp[i] = A[n-i-1];
      }
      return temp;
}

What is the the purpose of this method?

a.	To make an array that is a copy of the array A
b.	To make an array that is a copy of the array A in reverse order
c.	To make an array that is a scrambled copy of the array A
d.	To make an array that is filled with the negatives of the array A
e.	To make an array of random integers

Suppose the method int sign(int x) returns 1 if x is positive, -1 if x is negative and 0 if x is 0. Given

int[] nums = {-2, -1, 0, 1, 2};

what are the values of the elements of nums after the following code is executed?

for(int k=0; k<nums.length; k++)
{

nums[k] -= sign(nums[k]);
nums[k] += sign(nums[k]);

}

a.	-2, -1, 0, 1, 2
b.	-1, 0, 0, 0, 1
c.	0, 0, 0, 0, 0
d.	-2, 0, 0, 2, 3
e.	-2, 0, 0, 0, 2

Consider the following method:

// Returns true if there are duplicate values in
// the array parameter nums; false otherwise
public static boolean duplicates(int[] nums)
{
int j, k, n = nums.length;
<code>
}

Which of the following code segments can be used to replace <code> so that the method duplicates works as specified?

I.	for(j=0; j<n; j++) { for(k=j+1; k<n; k++) { if(nums[j]==nums[k]) return true; } } return false;
II.	for(j=1; j<n; j++) { for(k=0; k<j; k++) { if(nums[j]==nums[k]) return true; } } return false;
III.	for(j=0; j<n; j++) { for(k=0; k<n; k++) { if(nums[j]==nums[k]) return true; } } return false;

a.	I only	c.	I and II only	e.	I, II and III
b.	II only	d.	I and III only

What is the output of the following code segment?

String str1 = “Happy ”;
String str2 = str1;
str2 += “New Year! ”;
str1 = str2.substring(6);
System.out.println(str1 + str2)

a.	Happy New Year!
b.	Happy Happy New Year!
c.	New Year! New Year!
d.	New Year! Happy New Year!
e.	Happy New Year! Happy New Year!

Consider the following method:

public static String process(String msg, String s)
{
      int pos = msg.indexOf(s);
      msg = msg.substring(0,pos) + " " + s;
      return msg;
}

What is the output of the following code segment?

String s1 = "superstar";
String s2 = "star";
System.out.println(process(s1, s2));

a.	superstar
b.	superstarstar
c.	super star
d.	superstar star
e.	super starstar