北邮国院JAVA 1415年考题+答案

int counter = 0, numUsers = users.length; [1 mark]
do { if (users[counter].ID == userID) { found = true; }
counter++; [0.5 mark] } while (counter < numUsers); [1 mark]
Pre-increment example: [1.5 marks] A pre operation causes the variable to first be incremented or decremented and then it is used in the current statement.
int a = 5; int result = a + a++;
After executing the statements above, result=10.
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EBU4201 Paper A (Solutions)
2014/15
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public class TestClass { void doSomePrinting() { System.out.println("I Love Java"); } public static void main(String[] args) {
TestClass myClass = new TestClass(); [1 mark] myClass.doSomePrinting(); [1 mark]
iii) private access means that something is visible to (or within) the class only.
[1 mark] public access means that something is visible to the world [1 mark]. protected access means that something is visible to (or within) the package and all subclasses [1 mark].
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EBU4201 Paper A (Solutions)
ii) Approach 1: Instantiate the class TestClass first and then, access the instance
method doSomePrinting(). [1 mark]
int a = 5;
int result = a+ ++a;
After executing the statements above, result=11.
10 marks
b) Answer the questions below about code error resolving, javadoc, class instantiation and method call. [8 marks]
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ii)
byte
short
int
long
float
double
boolean
char
[8*0.5 mark: each correctly listed primitive data type]
iii) Post-increment example: [1.5 marks] A post operation causes the variable to be used ‘as is’ in the current statement and it is then incremented or decremented afterwards.
} }
2014/15
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Approach 2: Declare the method doSomePrinting() as static, and access it in the main() method without instantiation; this is not an object-oriented approach, so it is not good programming practice. [2 mark]
[7 marks]
i) In Java, how does an object relate to a class?
(1 mark)
ii) Describe the concept of overriding in Java.
(1 mark)
iii) What is the difference between the private, public and protected access modifiers? (3 marks)
2014/15 [7 marks]
for (int i=0; i<users.length; i++) { if (users[i].ID == userID) { found = true; break; }
} if (!found) {
// Add User } } }
Figure 2 i) Rewrite the addUser() method, using while and do-while loop approaches.
Figure 1
ii) Write Java code to demonstrate and explain TWO ways to resolve the problem found in part i). (6 marks)
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i) Calling the doSomePrinting() method in line 7 is invalid [1 mark], because it is not possible to call a non-static method from a static method [1 mark].
javac java javadoc jar
ii) List all the Java primitive data types.
iii) Using examples, explain both the post-increment and pre-increment operations.
[10 marks]
(3 marks) (4 marks) (3 marks)
i) javac – this is the Java compiler. [0.5 mark] java – This is launcher program for Java applications. [0.5 mark] javadoc – This is the API documentation generator. [1 mark] jar – This tool is used to manage Java Archive (JAR) files. [1 mark]
7 marks
Question marking: 10 8 7 25
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EBU4201 Paper A (Solutions)
2014/15
Question 2
a) Answer the questions below about basics concepts in Java:
int counter = 0, numUsers = users.length; [1 mark] while (counter < numUsers) { [1 mark]
if (users[counter].ID == userID) { found = true; }
counter++; [0.5 mark]
EBU4201 Paper A (Solutions)
2014/15
Question 1 a) Answer the questions below about basic Java concepts:
i) Briefly explain the purpose of each of the following Java tools:
} if (!found) {
// Add User } }
Do not write in thisr A (Solutions)
do-while loop approach:
public void addUser(int userID) { Boolean found = false;
1 public class TestClass {
2
void doSomePrinting() {
3
System.out.println("I Love Java");
4
}
5
6
public static void main(String[] args) {
7
doSomePrinting();
8
}
9}
ii) Explain the difference between while and do-while loops.
(5 marks) (2 marks)
i) while loop approach:
public void addUser(int userID) {