1) Give the Big O for the following:
a. n2 + 6n + 32
b. n +6
c. Analyze the code below for integer n:
while (n > 0) {
n = n/10; // Integer division
}
2) Explain in your own words - when is it appropriate to implement a static method? Give an example as part of your answer.
Answer: The best time to use a static method would be if a method needs to be in a class, but not tied to an object:
Example : class Languages { public static void main(String[] args) { display();
}
static void display()
{
System.out.println("Java is my favorite programming language."); }
}
3) Consider the following method with integer value x.
public static test(int x)
{
x += 2;
}
Suppose y has a value of 10, then the method is activated test(y) what is the value of y after this activation? The Value of Y will be 5.
4) Consider this code that creates some Location objects with coordinates x=10 and y=20:
Location a, b, c;
a = new Location(10,20);
b = new Location(10,20);
c = b;
...
After this code executes, what are the values of these boolean expressions?
a) a= =b
b) a.equals(b)
c) a= =c
d) a.equals(c)
e) b= =c
f) b.equals(c)
Also, explain the difference between == and the equals method for the Location class.
5) Write a code fragment (in Java) that creates an array 50 integers, and initializes each cell to the same value as its index number (i.e. [0] = 0, [1] = 1, etc.). [hint: use a loop]
6) What happens if you call new but the heap is out of memory?
7) Draw a picture of memory after these statements:
int[ ] m = new int[2];
m[0] = 0;
m[1] = 1;
int[ ] p = m;
p[0] = 4;
p[0] = 5
8) Consider the method:
public static test2(int[ ] b)
{
b[0]++;
}
Draw a picture of memory after these statements (also show what is printed out)
int[ ] x = new int[100];
x[0] = 2;
foo(x);
System.out.println(x[0]);
9) Describe (in English) the steps for inserting a new item at the head of a linked list? Make sure you consider all possible incoming conditions.
10) Write out the following method as a static method for the IntNode class (similar to the book: use data & link) public static int count10s (IntNode head)
// Precondition: Head is a reference to a linked list of integers,
// condition of the list is unknown (empty or not)
// Postcondition: Method returns number of 10s found in the linked list.
// list is unchanged.
11) Write out the following method as a static method for the IntNode class (similar to the book: use data & link)
public static void insertAtTail (IntNode head, int value)
// Precondition: Head is a reference to a linked list of integers,
// condition of the list is unknown (empty or not), int refers to value to be // added to the list at the END.
// Postcondition: List will have an additional node with the value placed in // it.
[Note] - break this into two parts - finding the right spot and then inserting. The insert you already described up above - you just need to look for the last node; that node's link can be looked at as the "head" to your new node. Don't forget to watch for empty case.
12) The following is a code fragment used to count the # of occurrences of a specific "target" integer in an array.
int i;
int answer = 0;
for (i = 0; i < data.length; i++)
if (data[i] == target)
answer++;
Answer of course is the # of times the target is found in the array. Rewrite the code so that it works correctly when the data array is an array of objects and target is a non-null reference to an object with an equals method.
13) Suppose that the variable head is a reference to the head node of a linked list of objects. Each node has an instance variable called link (which is a reference to the next node) and another instance variable called data (which is an Object that's stored in the node). Write a few lines of code to count the number of occurrences of a specific non-null target Object on the list. At the end of your code, a variable called answer should indicate how many times the target appears in the array. Use target.equals to test for equality.