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Miguel Gamboa edited this page Mar 6, 2024 · 7 revisions

Share your code with user fmcarvalho in a private Github repository named isel-lae-2024-your_number. Create a new folder for each homework.

Homework 01 - Metadata and Objects Layout (28-2-2024)

On folder lesson03-TPC run javap -p apps/Amber.class to analyze the metadata of Amber.class.

  1. Write in Java an equivalent class to the output produced by javap

  2. Make a prediction about the expected layout and size of an instance of the Amber class in the JVM 64-bit model, 8-byte alignment and no compressed references. Save your design in a file amber-layout.txt

  3. Verify your expectations in point 2 comparing it to the result of the output of JOL for Hotspot Layout Simulation (JDK 15, 64-bit model, NO compressed references, NO compressed classes, 8-byte aligned). Run JOL with:

java -cp .;jol-cli-0.17-full.jar org.openjdk.jol.Main estimates apps.Amber

NOTE: Replace ; by : on -cp if you are using a linux-based terminal

Homework 02 - Virtual Methods (6-3-2024)

Consider the following definition of types A, B, C, and I. Given the use of those types in main, answer the following questions:

  1. Predict the output of the execution of the main function.
  2. What are the differences in resulting output if we remove the final keyword from virtualFoo in class B?
  3. Keeping the definition of types A, B, C, and I as it is, what would be the result of adding the following implementation in class C:
    • public void virtualFoo() { out.println("C"); }
  4. Provide an equivalent implementation in Kotlin for types A, B, C, and I, with only the method virtualFoo to achieve the same result as in question 1. Do not include the static method foo.
interface I { void virtualFoo(); }
class A {
    public static void foo() { out.println("A"); }
    public void virtualFoo(){ out.println("B"); }
}
class B extends A implements I {
    public static void foo() { out.println("B"); }
    public final void virtualFoo(){ out.println("B"); }
}
class C extends B {
    public static void foo(){ out.println("C"); }
}
 
public static void main(String[] args) {
    final C c = new C();
    final A a = c;
    final B b = c;
    final I i = c;
    a.foo();
    a.virtualFoo();
    b.foo();
    b.virtualFoo();
    c.foo();
    c.virtualFoo();
    i.virtualFoo();       
}
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