Java Puzzlers

Сентябрь 7, 2022

Содержание

2. Oddity The following method tests whether its argument is odd: public static boolean isOdd(int i) {
3. Making change public class Change { public static void main(String[] args) { System.out.println(2.00 - 1.10); }
4. Long Division public class LongDivision { public static void main(String[] args) { final long MICROS_PER_DAY =
5. Addition public class Addition { public static void main(String[] args) { System.out.println(12345 + 5432l); } }
6. Tweedledum Declare variables x and i such that x += i; is legal, but x =
7. Tweedledee Declare variables x and i such that x = x + i; is legal, but
8. += public class PlusEquals { public static void main(String[] args) { int i = 2; i
9. Last Laugh public class LastLaugh { public static void main(String[] args) { System.out.print("H" + "a"); System.out.print('H'
10. Indecision public class Indecisive { public static void main(String[] args) { System.out.println(decision()); } static boolean decision()
11. HelloGoodbye public class HelloGoodbye { public static void main(String[] args) { try { System.out.println("Hello world!"); System.exit(0);
12. The reluctant constructor public class Reluctant { private Reluctant internalInstance = new Reluctant(); public Reluctant() throws
13. Hello again public class Null { public static void main(String[] args) { ((Null)null).greet(); } public static
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Слайд 2

Oddity
The following method tests whether its argument is odd:
public static boolean

isOdd(int i) { return i % 2 == 1; }
Does it work?
It gives the correct answer for ¾ of the integers

Слайд 3

Making change
public class Change { public static void main(String[] args) {

System.out.println(2.00 - 1.10); } }
0.8999999999999999

Слайд 4

Long Division
public class LongDivision { public static void main(String[] args) {

final long MICROS_PER_DAY = 24 * 60 * 60 * 1000 * 1000; final long MILLIS_PER_DAY = 24 * 60 * 60 * 1000; System.out.println(MICROS_PER_DAY / MILLIS_PER_DAY); } }
5

Слайд 5

Addition
public class Addition { public static void main(String[] args) { System.out.println(12345

+ 5432l); } }
17777

Слайд 6

Tweedledum
Declare variables x and i such that x += i; is legal,

but x = x + i; is not legal
short x = 0; int i = 123456;

Слайд 7

Tweedledee
Declare variables x and i such that x = x +

i; is legal, but x += i; is not legal
Object x = "Hello "; String i = "world!";

Слайд 8

+=
public class PlusEquals { public static void main(String[] args) { int

i = 2; i += 3.75; System.out.println(i); } }
5

Слайд 9

Last Laugh
public class LastLaugh { public static void main(String[] args) {

System.out.print("H" + "a"); System.out.print('H' + 'a'); } }
Ha169

Слайд 10

Indecision
public class Indecisive { public static void main(String[] args) { System.out.println(decision());

} static boolean decision() { try { return true; } finally { return false; } } }
false

Слайд 11

HelloGoodbye
public class HelloGoodbye { public static void main(String[] args) { try

{ System.out.println("Hello world!"); System.exit(0); } finally { System.out.println("Goodbye world!"); } } }
Hello world!

Слайд 12

The reluctant constructor
public class Reluctant { private Reluctant internalInstance = new

Reluctant(); public Reluctant() throws Exception { throw new Exception("I'm not coming out!"); } public static void main(String[] args) { try { Reluctant b = new Reluctant(); System.out.println("Surprise!"); } catch (Exception e) { System.out.println("I told you so."); } } }
Exception in thread "main" java.lang.StackOverflowError

Слайд 13

Hello again
public class Null { public static void main(String[] args) {

((Null)null).greet(); } public static void greet() { System.out.println("Hello world!"); } }
Hello world!

Java Puzzlers

Содержание

OddityThe following method tests whether its argument is odd:public static boolean

Making changepublic class Change { public static void main(String[] args) {

Long Divisionpublic class LongDivision { public static void main(String[] args) {

Additionpublic class Addition { public static void main(String[] args) { System.out.println(12345

TweedledumDeclare variables x and i such that x += i; is legal,

TweedledeeDeclare variables x and i such that x = x +

+=public class PlusEquals { public static void main(String[] args) { int

Last Laughpublic class LastLaugh { public static void main(String[] args) {

Indecisionpublic class Indecisive { public static void main(String[] args) { System.out.println(decision());

HelloGoodbyepublic class HelloGoodbye { public static void main(String[] args) { try

The reluctant constructorpublic class Reluctant { private Reluctant internalInstance = new

Hello againpublic class Null { public static void main(String[] args) {

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