Vize tekrar: 1-9. haftalar karışık

What is printed?

class Item {
    static int made = 0;
    int id;
    Item() { this(100); System.out.print("I() "); }
    Item(int id) { this.id = id + made; made++; System.out.print("I(" + this.id + ") "); }
}
// in main:
new Item(); new Item(5);
System.out.println(Item.made);

What is printed by new Mid();?

class Base {
    Base() { System.out.print("Base "); show(); }
    void show() { System.out.print("B.show "); }
}
class Mid extends Base {
    String tag = "mid";
    Mid() { super(); System.out.print("Mid "); }
    @Override void show() { System.out.print("M.show(" + tag + ") "); }
}

What is printed?

interface Scorable {
    int score();
    default String grade() { return score() >= 50 ? "PASS" : "FAIL"; }
}
abstract class Exam implements Scorable {
    protected int raw;
    Exam(int raw) { this.raw = raw; }
    public String toString() { return getClass().getSimpleName() + ":" + score() + ":" + grade(); }
}
class Midterm extends Exam { Midterm(int r) { super(r); } public int score() { return raw * 2; } }
class Final extends Exam {
    Final(int r) { super(r); }
    public int score() { return raw + 10; }
    public String grade() { return score() >= 60 ? "PASS" : "FAIL"; }
}
// in main:
Exam[] exams = { new Midterm(30), new Final(45), new Midterm(20) };
for (Exam e : exams) System.out.println(e);

Find the compile errors.

interface Scorable { int score(); }
abstract class Exam implements Scorable { }
class Quiz extends Exam { }
// in main:
Exam e = new Quiz();
Scorable s = e;
Quiz q = s;

What is printed?

static String mystery(String s) {
    StringBuilder sb = new StringBuilder();
    for (int i = s.length() - 1; i >= 0; i -= 2) sb.append(s.charAt(i));
    return sb.toString().toUpperCase();
}
// in main:
System.out.println(mystery("polymorph"));

What is printed?

String s = "a-b--c";
System.out.println(s.split("-").length + " " + s.replaceAll("-+", "+") + " " + s.indexOf("--"));

What is printed?

class Parser { int parse(String s) { return Integer.parseInt(s); } }
class SafeParser extends Parser {
    @Override int parse(String s) {
        try { return super.parse(s); }
        catch (NumberFormatException e) { return -1; }
        finally { System.out.print("[done " + s + "] "); }
    }
}
// in main:
Parser p = new SafeParser();
System.out.println(p.parse("12") + p.parse("x"));

What is printed?

static int risky(int x) {
    try {
        if (x < 0) throw new IllegalArgumentException("neg");
        return 10 / x;
    } catch (ArithmeticException e) {
        System.out.print("AE ");
        return 0;
    } finally {
        System.out.print("F ");
    }
}
// in main:
System.out.println(risky(5));
System.out.println(risky(0));
try { System.out.println(risky(-1)); }
catch (IllegalArgumentException e) { System.out.println("caught " + e.getMessage()); }

What is printed?

class Coin {
    int value;
    Coin(int v) { value = v; }
    public boolean equals(Coin other) { return value == other.value; }
}
// in main:
Coin c1 = new Coin(5), c2 = new Coin(5);
Object o2 = c2;
System.out.println(c1.equals(c2) + " " + c1.equals(o2));

Which statement is FALSE?

1. A subclass constructor always calls a superclass constructor first
2. An interface can contain default methods
3. A checked exception must be caught or declared
4. Fields are chosen by the object's runtime type

Which layout is the default for a JFrame's content pane, and what happens when you call frame.add(b1); frame.add(b2);?

Write an abstract class Shape that implements Comparable<Shape> (comparing by area) with an abstract double area(), and two subclasses Rect(w, h) and Circle(r). Sorting {Rect(2,5), Circle(1), Rect(1,1)} must give [Rect(1.0), Circle(3.14), Rect(10.0)].