1. Indicate which variant of foo will be called or write "error."
class AAA {
void foo(int x, boolean y) { ... } //v1
void foo(double y) { ... } // v2
}
class BBB extends AAA {
void foo(boolean x, int y) { ... } //
v3
void foo(double z) { ... } // v4
public static void main(String[] args)
{
AAA x = new AAA();
AAA y = new BBB();
BBB z = new BBB();
x.foo(3, false);
x.foo(10);
y.foo(3, false);
y.foo(true, 2);
y.foo(10);
z.foo(3, false);
z.foo(true, 2);
z.foo(10);
}
}
2. An observation has a time and an observed value. Time and value are real numbers. Two observations are equal if they have the same time and value. Here's an example of creating and displaying a set of observations:
Set<Observation> experiment = new
HashSet<Observation>();
experiment.add(new Observation(98.6, 30));
experiment.add(new Observation(98.6, 40));
experiment.add(new Observation(98.6, 40));
System.out.println(experiment);
The output produced is:
[98.6 @ 40.0, 98.6 @ 30.0]
Implement the Observation class. Be sure to include all of the necessary bookkeeping methods and overrides so that the indicated output will be produced.
3. A software company requires each class to have a non-static, parameterless method called test. This method tests the class and returns true if the class passes the test and false otherwise.
Complete the implementation of the following test driver:
class TestDriver {
public boolean
test(Collection<String> classNames) { ??? }
}
TestDriver.test gets a collection of class names as its input. It loads each class and invokes its test method. If all of the tests pass, true is returned, otherwise false is returned. Note: All tests must be run, even if some fail.
3. A group of monsters attack a hero. They take turns decrementing the hero's health until the hero dies (health == 0). The monsters must not attempt to decrement the hero's health at the exact same time, and the monsters must be cooperative. Here's the implementation of the Warrior class:
class Warrior {
private int health = 100;
public void addHealth(int amt) { health
+= amt; }
public void subHealth(int amt) { health
-= amt; }
public int getHealth() { return health;
}
}
Finish the implementation of Monster:
class Monster extends Thread {
private static Warrior hero = new
Warrior();
// etc.
}
4. A command is anything that implements the Command interface:
interface Command {
Object execute(); // returns null or a
result
}
There are four types of commands: Condition, Iteration, Expression, and Block. A condition has the form
if (EXPRESSION) COMMAND else COMMAND
An iteration has the form:
while (EXPRESSION) COMMAND
A block is a sequence of one or more commands of the form:
{COMMAND; ...; COMMAND;}
Executing an expression returns a result. For example, executing the expression "3 < 2" returns the result false; executing all other types of commands returns null.
A. Draw a UML class diagram showing how the concepts mentioned are related.
B. Implement the Block class.