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Assignment 8: Refactoring Solved
For the assignment, you will need to find out information about refactoring patterns, which does not appear in the lecture slides. The following location is an excellent starting point:http://www.refactoring.com/catalog/index.html.
1. Consider the following two code fragments.
Which fragment is more understandable? And why? (Hint: Think code smells)
A.
doublepotentialEnergy(double mass, double height) {
return mass * height * 9.81;
}
B.
static final double g = 9.81;
doublepotentialEnergy(double mass, double height) {
return mass * g * height;
1 of 7 2018-12-22, 9:21 p.m.
Assignment https://eclass.srv.ualberta.ca/mod/assign/view.php?id=3237750
}
2. Consider the following code fragment.
publicintfunny(int a, int b) {
int temp = a * b;
if (temp > 100) {
return temp * 0.95;
} else {
return temp * 0.25;
}
}
Apply the following refactoring patterns to this code fragment:
A. Inline Temp
B. Extract Method Followed by Replace Temp with Query
C. Discuss the two new code fragments, which refactoring pattern is more appropriate in this situation? And why?
3. Consider the following two code fragments.
A.
privateint currentBalance;
intwithdrawFromBankAccount(int amountToBeWithdrawn) {
if (amountToBeWithdrawn > currentBalance)
return -1;
else {
currentBalance -= amountToBeWithdrawn;
return 0;
}
}
2 of 7 2018-12-22, 9:21 p.m.B.
privateint currentBalance;
voidwithdrawFromBankAccount(int amountToBeWithdrawn) throws BalanceException { if (amountToBeWithdrawn > currentBalance)
throw new BalanceException();// You can assume that BalanceException is defined
currentBalance -= amountToBeWithdrawn;
}
Which refactoring pattern has been applied to the first fragment to transform it into the second code fragment? Explain why the second code fragment is superior to the first fragment.
4. Consider the following two code fragments (adaptedfrom java.lang.Long ).
A.
public static Long valueOf(long l) {
final int offset = 128;
if (l >= - 128 && l <= 127) {// will cache
return LongCache.cache[(int) l + offset];
}
return new Long(l);
}
B.
3 of 7 2018-12-22, 9:21 p.m.
Assignment https://eclass.srv.ualberta.ca/mod/assign/view.php?id=3237750
public static Long valueOf(long l) {
if (l >= - 128 && l <= 127) {// will cache
return LongCache.cache[(int) l + 128];
}
return new Long(l);
}
Fragment A is translated into Fragment B by applying the Inline Temp refactoring; and Fragment B is translated into Fragment A by applying the Introduce Explaining Variable refactoring. Provide possible situations (or contexts) where it would be advantageous to apply either refactoring to the appropriate code fragment.
5. Consider the following two code fragments.
A.
public class A {
public intk(long i) {
return 10;
}
}
public class B extends A {
public intk(int i) {
return 20;
}
public static voidmain(String[] args) {
System.out.println(new A().k(2));
}
}
B.
4 of 7 2018-12-22, 9:21 p.m.public class A {
public intk(long i) {
return 10;
}
public intk(int i) {
return 20;
}
}
public class B extends A {
public static voidmain(String[] args) {
System.out.println(new A().k(2));
}
}
Which refactoring pattern has been applied to the first fragment to transform it into the second code fragment? Explain the impact (upon the results from function test) of the transformation.
