PPT Slide

CS100A Answers to Sample #1

Question 1. 3 points for each correct answer.

For each question, we list only the final

values of variables that change.

(a) a: 12 (f) x: false

(b) a: 3 (g) x: false

(c) b: 3 (h) x: false

(d) (i) a: 6, b: 7

(e) a: 4

Question 2.

(a) 8 points. Class: a “model” or blueprint

for the objects (or instances) of the class; a class

defines the fields (or variables) and methods of

each object of the class.

(b) 8 points. Let c be any instance of class C. If field

or method x declared in C is private, x can be referenced

only in the code of class C; if protected, in class C or any

of its subclasses; if public, then in any code that can

reference instance c.

(c) 8 points. A function is a method that performs some task

and returns a value. Instead of the keyword void, the type or

class of the return value is used. Example:

// Yield x + y

public int plus (int x, int y)

{return x+y;}

(d) 8 points.

public class C

{private int x;

public int y;

public C(int x, int a)

{x= a;

y= x;

}

public String toString()

{x= 5;

z= 6;

int x= 4;

int z= 7;

x= y;

}

}

Question 3. 15 points. Here’s the body of drawCircle:

{g.drawOval(x-r,y-r,2*r,2*r);}

Question 4. (a) 5 points.

(b) 5 points.

Question 5. 25 points.

public class ContractEmployee extends Employee

{double dailyRate; // Daily rate of pay

double daysWorked; // Days worked in year

// Constructor: An employee with name n, d days of work,

// and s dollars per day

public ContractEmployee(String n, int d, double s)

{super (d*s, n);

dailyRate= s;

daysWorked= d;

}

// Yield a description of the contract employee

public String toString();

{return “Contract employee “ + name + “ days ” +

daysWorked + “ rate “ + dailyRate + “ = “ + pay;

}

// Change number of days worked to n

public void changeDays(int n)

{daysWorked= n;

pay= dailyRate*daysWorked;

}

}

b

Could

be

omitted

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