Question 1 [20 points]

Transcription

1 Question 1 [20 points] Explain following features of Eclipse IDE. Provide a very short example for each. a) Assume a class Student that represents a student of ECE department at UPRM. Give two different sets of instance variables and two different methods that can be used for implementing the Student class. Show which ones are defined private and which ones are defined public. Note: you need not to implement this class or any of its methods. Instance variables: private String name; private final long studid; Or private Name studentname; private final Id studid; Methods: public String getname(); public float gpa(); b) Show the body of a method Square (midx and midy, length) that calls one of the Rectangle constructors to construct a square. Note: midx and midy are the coordinate of the center of the square. topleftx=midx length / 2; toplefty=midy length / 2; Rectangle square=new Recatangle (topleftx, toplefty, length, length); c) Name one accessor and one mutator method of the String class. accessor method: replace; String class does not have a mutator method; d) Explain the feature of Help Cheat Sheets in Eclipse IDE with a very short example. To produce a help (similar to a cheat sheet) by opening a selection dialog that can be used as a quick reference. Example: it can show how to write a Hello World application. Page 1/5

2 Question 2 [20 points] Write an algorithm (flowchart or pseudo-code) that receives an integer number and determines if it is autoreverse or not. We call an integer number an autoreverse number if it reads the same from left to right and from right to left. Three examples of autoreverse numbers are 5005, , and 6. Three examples of numbers that are not autoreverse are 5050, , and 18. === 1. Receive n; 2. Compute reverse of n; 3. if reverse of n equals to n then print ( yes, n is autoreverse ) else print ( no, n is not autoreverse ); 4. end. To computer reverse of n: 1. reverse 0; 2. While n>0 do 2.1 reverse=reverse * 10 + (n module 10); 2.2 n= integer division of (n / 10); 3. end of while; 4. end. Assumption: we assumed n is a positive number. Page 2/5

3 Question 3 [20 points] Write an algorithm (flowchart or pseudo-code) that receives a binary representation of the fractional part of a number and converts it to the decimal representation. For example, if the input is 0.101, the output should be Recall: to convert to decimal representation, the calculations are as 1*(2-1 )+0*(2-2 )+1*(2-3 ) As another example, to convert to decimal representation, the calculations are as follows: 1*(2-1 )+0*(2-2 )+ 0*(2-3 )+ 0*(2-4 )+ 1*(2-5 )+1*(2-6 )+ 0*(2-7 )+ 1*(2-8 ) 1. Receive nbinary; 2. i -1; 3. ndecimal 0 ; 4. While nbinary>0 4.1 digit integer part of (nbinary *10); 4.2 ndecimal ndecimal + digit * 2 i ; 4.3 i i-1; 4.4 nbinary nbinary*10 digit; 5. End of while; 6. Print ndecimal 7. End. Page 3/5

4 Question 4 [20 points] Write a program in Java that defines a new class of numbers called SpecialNum. Each object of this class has an integer value. Furthermore, this class has three methods, namely reverse, autoreverse, and getvalue. Method reverse returns the reverse of the integer value of the object.. Method autoreverse determines if an object of class SpecialNum is auto-reversal or not by returning either true or false. Note: Provide appropriate documentation. public class SpecialNum { * Constructs a special number that its integer value is x public SpecialNum (int x){ this.x=x; * returns the reverse of an integer value public int reverse(){ int x=0, temp=this.x; while (temp>0){ x=x*10+ (temp % 10); temp=temp / 10; return x; * if the integer value of an object is equal to its reverse * autoreverse returns TRUE public boolean autoreverse(){ if (x==this.reverse()) return true; else return false; * rtuens the integer value of a special number public int getvalue(){ return x; * the integer value of the object private int x; Page 4/5

5 Question 5 [20 points] Write a program in Java that receives a binary representation of the fractional part of a number and prints its (approximate) decimal representation. For example, if the input is 0.101, the output should be Note: you may want to see Question 3 for more information about how to convert a fractional part from the binary representation to the decimal representation. Note: Provide appropriate documentation. package BinaryNum; import java.util.scanner; * Class BinaryNum is to show how a binary fraction * can be converted to its equivalent decimal representation public class BinaryNum { * Receives the fractional part of a number in binary representation * and prints its decimal representation equivalent. arg public static void main (String[] arg) { Scanner in=new Scanner(System.in); Double x= in.nextdouble(); System.out.println("Binary representation: "+x); System.out.println("Decimal representation: "+todecimal(x)); * converts binay fraction to decimal fraction binaryrep is the binary representation of * the fractional part of a number its decimal equivalent public static double todecimal(double binaryrep) { int digit=0, i=-1; double decimal=0; while (binaryrep>0) { digit=(int) (binaryrep*10); decimal=decimal+digit* Math.pow(2,i); i--; binaryrep=binaryrep*10-digit; return decimal; Page 5/5