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Assignment1 Answer(More than the assignment needed!!)
1.
Suppose a and b are int variables. What is the value of b?
a = 3;
b = 4 + (++a);
Answer:
2.
8
Given the following assignments. What is the value in str?
String str;
str
= “Hello”;
str = str + “ World”;
Answer: Hello World
3.
The method showInputDialog belongs to the class ____.
Answer: JOptionPane
4.
The tokens of a string are usually delimited by ____ characters.
Answer: whitespace
5.
What is the value of the expression:
(10 >= 5) && (‘B’ < ‘C’)
Answer: true
6.
With short-circuit evaluation, when the value of an entire expression is found, evaluation ____.
Answer: stops
7.
Write a Java statement to accomplish each of the following tasks
a) Declare variables x, y, z, thisIsAVariable, q76354 and number to be of type int
Answer:
int x, y, z, thisIsAVariable, q76354, number;
b) Declare the variables xVal, yVal and zVal to be of type String.
Answer:
String xVal, yVal, zVal;
c) Convert xVal to an int and store the result in the variable x
Answer:
x = Integer.parseInt(xVal);
8.
Rewrite the following if-else statement using switch statement.
if (florida == 1) {
System.out.println("Number 1 Ranking!");
}
else if(florida == 2) {
System.out.println("Almost there ...");
}
else {
System.out.println("Unacceptable");
[16 marks]
}
Answer :
switch(florida)
{
case 1: System.out.println("Number 1 Ranking!");
break;
case 2: System.out.println("Almost there ... ");
break;
default: System.out.println("Unacceptable");
}
9.
What is the result of running the following piece of code?
import java.util.*;
public class Test{
public static void main(String args[]){
String s = new String("Java~see~Java~do");
StringTokenizer st = new StringTokenizer(s, "/");
int count = 1;
while(st.hasMoreTokens()){
System.out.println("Token number " + count + " : " + st.nextToken());
count++;
}
}
}
Answer :
Java~see~Java~do
10
Assume that the way the StringTokenizer is created in the above sample program is changed as follows:
StringTokenizer st = new StringTokenizer(s, "~");
What is the result of the sample program?
import java.util.*;
public class Test{
public static void main(String args[]){
String s = new String("Java~see~Java~do");
StringTokenizer st = new StringTokenizer(s, "~");
int count = 1;
while(st.hasMoreTokens()){
System.out.println("Token number " + count + " : " + st.nextToken());
count++;
}
}
}
Answer :
Token number 1 : Java
Token number 2 : see
Token number 3 : Java
Token number 4 : do
11
Rewrites the following program segment by using a while and a do … while loop to have the same output.
j = 2;
For(i = 1;i<=5;i++){
System.out.print(j + “ ”);
j= j+5;
}
System.out.println();
Ans
a.
j = 2;
i = 1;
while(i <= 5)
{
System.out.print(j + " ");
j = j + 5;
i++;
}
System.out.println();
b.
j = 2;
i = 1;
do
{
System.out.print(j + " ");
j = j + 5;
i++;
} while(i <= 5);
System.out.println();
12
What is the output of the following Java code?
x=100;
y=200;
if(x>100 && y<=200)
System.out.println(x + “ ” + y + “ ” + (x+y));
Else
System.out.println(x + “ ” + y + “ ” + (2*x-y));
Ans:
100 200 0
Suppose that you have the following declaration:
int j = 0;
The output of the statement
if ((8>4 || (j++ ==7)))
System.out.println(“j =” +j);
is:
j=0
while the output of the statement
if ((8>4 | (j++ ==7)))
System.out.println(“j =” +j);
is:
j=1
Explain why?
Ans: The expression ((8 > 4) || (j++ == 7)) is evaluated using short circuit. Because 8 > 4 is true, the
expression (j++ == 7) is not evaluate. Therefore, the value of j stays 0. On the other hand, to evaluate the
expression ((8 > 4) | (j++ == 7)) no short circuit is used. Therefore, both the expressions (8 > 4) and (j++
== 7)) are evaluated. The expression j++ increments the value j by 1.
13
Suppose that str is a String variable. Write a Java statement that uses the operator new to instantiate the object
str and assign the string “Java Programming” to str.
Ans:
str = new String (“Java Programming”)
14
Consider the following statements:
String str = “Going to the amusement park.”;
char ch;
int len;
int position;
a.
What value is stored in ch by the following statement?
ch = str.charAt(0);
The value stored in ch is ‘G’.
b.
What value is stored in ch by the following statement?
ch = str.charAt(11);
The value stored in ch is ‘e’.
c.
What value is stored in len by the following statement?
len = str.length();
The value stored in len is 28.
d.
What value is stored in position by the following statement?
position = str.indexOf(‘t’);
The value stored in position is 6
15
Rewrite the following decision statement using the conditional operator (?:).
If(page == odd)
System.out.println(“This is an odd page.”);
else
System.out.println(“This is an even page.”);
(5 marks)
Ans: System.out.println(“This is an “ + (page==odd ? “odd” : “even ”) + “page.”);
16
Assume the following statements:
String str;
String str1 = “diploma”;
String str2;
String str3;
str
= “Java programming: second programming module for diploma courses”;
What are the value of the following expressions?
(a) str.indexOf(“module”)
(b) str.substring(5, 16);
(c) str.startsWith(“Java”)
(d) str.startsWith(“J”)
(e) str.endsWith(“.”)
(f) str.regionMatches(48, str1, 0, str1.length());
(g) str.regionMatches(true, 31, “module”, 0, 6);
Note: the method header of regionMathces() are
Boolean regionMatches(int index, String str, int strIndex, int len);
Boolean regionMatches(boolean ignorcase, int index, String str, int strIndex, int len);
Ans:
(a) 37
(b) programming
(c) true
(d) true
(e) false
(f) true
(g) false
17
What is the result of the following piece of code?
public class C8Q9{
public static void main(String args[]){
if( 3 > 4 | 4 > 1 | 1 == 0){
System.out.println(" OR condition satisfied");
}
else{
System.out.println(" OR condition not satisfied");
}
}
}
Ans:
OR condition satisfied
18
What is the output of the following piece of code?
public class C8Q3{
public static void main(String args[]){
int i = 100;
System.out.println("Result: " + (( i < 100 ) ? 20.8 : 10 ));
}
}
Result: 10.0
19
The difference between char and Character is
Ans:
char is a primitive type; Character is a class