Section Name: Leader:
Edward Leon Knapp
Pre-Lab 04 CSC 127A Spring 2008 (10 points)
1. What is null? When do you set objects equal to null? Null is the term for when an object reference is first declared, but hasn't been assigned to an object. When an object is set to null, an error appears named "exception." 2. Find a static method in the API and describe why it is static and what it is used for. Static data belongs to a class, rather than a particular object. We use the static method to define constants for commonly used values.
3.
Describe the differences between double and Double. Double converts a String to a Double object and returns that object whereas a double converts a String to a double and returns the value.
4.
What is the difference between sequential execution and selection? Selection allows the programmer to test for certain conditions and to select instructions to execute based on results of the test. Sequential execution makes the program use the information that is given in order.
5.
Which data types can be compared using the equality operators? Which ones cannot? Be specific. Equality operators only work if the two things being used to compare two of the same objects. Therefore, if two objects or object classes are equal, means it the values are the same, and the output will be true.
6.
What methods can one use to compare two Strings? Some of the methods to compare Strings are boolean and int. Both compare the values of Strings but they compare different aspects of the strings.
Name: Section Leader:
Edward Leon Knapp
7.
When does an if statement terminate? An "if" statement terminates if it does not have to right true or false information to base an answer off of. The criteria need to be determined for the statement to produce an answer.
8.
Why does the else not have a condition like the if does? The main difference between an if and an else statement is that the else statement does not
require a false block. The else statement skips over the false statement. 9. Using the if/else structure, write the pseudocode for determining if a number is even or odd If ( divisor == 2) System.out.println("Sorry; unable to divide by 2"); Else System.out.println("if dividend cannot be divided by 2, it is not even") 10. Explain in detail why it makes no sense to put a semi-colon at the end of an if statement header.
When a semi-colon is used at the end of a if statement, it makes it an incorrect statement which causes the program to not work.