Fixing Java puzzlers

docs/exPuzzlers/src/_02_expressive/_01_Oddity/Oddity.java

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+package _02_expressive._01_Oddity;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 5). Pearson Education (USA). Kindle Edition.
+ */
+public class Oddity {
+    public static boolean isOdd(int i) {
+        return i % 2 == 1;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(isOdd(-1));
+    }
+}

docs/exPuzzlers/src/_02_expressive/_02_Time_for_a_Change/BigDecimalSolution.kt

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+namespace change
+
+import java.math.BigDecimal
+import std.io.*
+
+fun main(args : Array<String>) {
+  // Easy to make BigDecimals user-friendly
+  println(
+    "2.00".bd - "1.00"
+  )
+}
+
+val String.bd = BigDecimal(this)
+
+fun BigDecimal.minus(other : BigDecimal) = this.subtract(other)
+fun BigDecimal.minus(other : String) = subtract(other.bd) // this can be omitted
+
+
+

docs/exPuzzlers/src/_02_expressive/_02_Time_for_a_Change/Change.java

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+package _02_expressive._02_Time_for_a_Change;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 7). Pearson Education (USA). Kindle Edition.
+ */
+public class Change {
+    public static void main(String args[ ] ) {
+        System.out.println(2.00 - 1.10);
+    }
+}
+

docs/exPuzzlers/src/_02_expressive/_02_Time_for_a_Change/ChangeSolutions.java

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+package _02_expressive._02_Time_for_a_Change;
+
+import java.math.BigDecimal;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 7). Pearson Education (USA). Kindle Edition.
+ */
+public class ChangeSolutions {
+    public static void main(String args[ ] ) {
+        // Poor solution - still uses binary floating-point!
+        System.out.printf("%.2f%n", 2.00 - 1.10);
+
+        // Calculation in cents
+        System.out.println((200 - 110) + " cents");
+
+        // BigDecimal
+        System.out.println(new BigDecimal("2.00"). subtract(new BigDecimal("1.10")));
+    }
+}
+

docs/exPuzzlers/src/_02_expressive/_03_Long_Division/LongDivision.java

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+package _02_expressive._03_Long_Division;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 9). Pearson Education (USA). Kindle Edition.
+ */
+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);
+    }
+}

docs/exPuzzlers/src/_02_expressive/_03_Long_Division/LongDivision.kt

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+namespace long.division
+
+import std.io.*
+
+fun main(args : Array<String>) {
+    // Problematic case does not compile
+//    val MICROS_PER_DAY_ : Long = 24 * 60 * 60 * 1000 * 1000;
+//    val MILLIS_PER_DAY_ : Long = 24 * 60 * 60 * 1000
+
+    // Solution:
+    val MICROS_PER_DAY : Long = 24.lng * 60 * 60 * 1000 * 1000;
+    val MILLIS_PER_DAY : Long = 24.lng * 60 * 60 * 1000
+
+    println(MICROS_PER_DAY / MILLIS_PER_DAY)
+}

docs/exPuzzlers/src/_02_expressive/_03_Long_Division/LongDivisionSolution.java

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+package _02_expressive._03_Long_Division;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 9). Pearson Education (USA). Kindle Edition.
+ */
+public class LongDivisionSolution {
+    public static void main(String[] args) {
+        final long MICROS_PER_DAY = 24L * 60 * 60 * 1000 * 1000;
+        final long MILLIS_PER_DAY = 24L * 60 * 60 * 1000;
+        System.out.println(MICROS_PER_DAY / MILLIS_PER_DAY);
+    }
+}

docs/exPuzzlers/src/_02_expressive/_03_Long_Division/LongDivisionSolution.kt

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+namespace long.division.solution
+
+import std.io.*
+
+fun main(args : Array<String>) {
+    val MICROS_PER_DAY : Long = 24.lng * 60 * 60 * 1000 * 1000;
+    val MILLIS_PER_DAY : Long = 24.lng * 60 * 60 * 1000
+
+    println(MICROS_PER_DAY / MILLIS_PER_DAY)
+}

docs/exPuzzlers/src/_02_expressive/_04_Elementary/Elementary.java

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+package _02_expressive._04_Elementary;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 11). Pearson Education (USA). Kindle Edition.
+ */
+public class Elementary {
+    public static void main(String[] args) {
+        System.out.println(12345 + 5432l);
+    }
+}
+

docs/exPuzzlers/src/_02_expressive/_04_Elementary/Elementary.kt

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+namespace elementary
+
+import std.io.*
+
+fun main(args : Array<String>) {
+    // Problematic case does not compile
+//    println(12345 + 5432l)
+
+    // Correct syntax:
+    println(12345 + 5432.lng)
+}

docs/exPuzzlers/src/_02_expressive/_04_Elementary/ElementarySolution.java

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+package _02_expressive._04_Elementary;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 11). Pearson Education (USA). Kindle Edition.
+ */
+public class ElementarySolution {
+    public static void main(String[] args) {
+        System.out.println(12345 + 5432L);
+    }
+}
+

docs/exPuzzlers/src/_02_expressive/_05_The_Joy_of_Hex/JoyOfHex.java

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+package _02_expressive._05_The_Joy_of_Hex;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 13). Pearson Education (USA). Kindle Edition.
+ */
+public class JoyOfHex {
+    public static void main(String[] args) {
+        System.out.println(Long.toHexString(0x100000000L + 0xcafebabe));
+    }
+}
+

docs/exPuzzlers/src/_02_expressive/_06_Multicast/Multicast.kt

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+namespace multicast
+
+import std.io.*
+
+fun main(args : Array<String>) {
+    println(-1.byt.chr.int)
+    println((-1).byt.chr.int)
+}

docs/exPuzzlers/src/_02_expressive/_06_Multicast/Mutlicast.java

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+package _02_expressive._06_Multicast;
+
+/**
+ * @author abreslav
+ */
+public class Mutlicast {
+    public static void main(String[] args) {
+        System.out.println((int) (char) (byte) -1);
+    }
+}
+

docs/exPuzzlers/src/_02_expressive/_07_Swap_Meat/CleverSwap.java

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+package _02_expressive._07_Swap_Meat;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 17). Pearson Education (USA). Kindle Edition.
+ */
+public class CleverSwap {
+    public static void main(String[] args) {
+        int x = 1984; // (0x7c0)
+        int y = 2001; // (0x7d1)
+        x ^= y ^= x ^= y;
+        System.out.println("x = " + x + "; y = " + y);
+
+        // Solution: swap with a temp variable
+        // Do not assign to the same variable more than once in a single expression.
+    }
+}

docs/exPuzzlers/src/_02_expressive/_07_Swap_Meat/CleverSwap.kt

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+namespace cleverswap
+
+import std.io.*
+
+fun main(args : Array<String>) {
+    var x = 1
+    // Do not assign to the same variable more than once in a single expression.
+    // Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 19). Pearson Education (USA). Kindle Edition.
+//    x += (y += z)
+}

docs/exPuzzlers/src/_02_expressive/_08_Dos_Equis/DosEquis.java

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+package _02_expressive._08_Dos_Equis;
+
+/**
+ * @author abreslav
+ */
+public class DosEquis {
+    public static void main(String[] args) {
+        char x = 'X';
+        int i = 0;
+        System.out.print(true ? x : 0);
+        System.out.print(false ? i : x);
+    }
+}

docs/exPuzzlers/src/_02_expressive/_08_Dos_Equis/DosEquis.kt

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+namespace dos.equis
+
+import std.io.*
+
+fun main(args : Array<String>) {
+    // Problematic case does not compile
+    val x = 'X'
+    val i = 0
+    print(if (true) x else 0)
+    print(if (false) 0 else x)
+
+    // Mixed computations do not compile:
+//    val int : Int = if (true) x else 0
+//    val char : Char = if (false) 0 else x
+}

docs/exPuzzlers/src/_02_expressive/_09_Tweedledum/Tweedledum.java

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+package _02_expressive._09_Tweedledum;
+
+/**
+ * @author abreslav
+ */
+public class Tweedledum {
+    public static void main(String[] args) {
+        byte x = 1;
+        byte i = 1;
+        x += i;
+//        x = x + i;
+    }
+}

docs/exPuzzlers/src/_02_expressive/_10_Tweedledee/Tweedledee.java

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+package _02_expressive._10_Tweedledee;
+
+/**
+ * @author abreslav
+ */
+public class Tweedledee {
+    public static void main(String[] args) {
+        Object x = 1;
+        String i = "1";
+//        x += i;
+        x = x + i;
+    }
+}

docs/exPuzzlers/src/_03_character/_11_The_Last_Laugh/LastLaugh.java

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+package _03_character._11_The_Last_Laugh;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 25). Pearson Education (USA). Kindle Edition.
+ */
+public class LastLaugh {
+    public static void main(String args[]) {
+        System.out.print("H" + "a");
+        System.out.print('H' + 'a');
+    }
+}
+

docs/exPuzzlers/src/_03_character/_11_The_Last_Laugh/LastLaugh.kt

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+namespace last.laugh
+
+import std.io.*
+
+fun main(args : Array<String>) {
+    print("H" + "a")
+    // Problematic case does not compile
+//    System.out?.print('H' + 'a')
+
+    // Solution
+    print('H'.toString() + 'a')
+}

docs/exPuzzlers/src/_03_character/_12_ABC/Abc.java

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+package _03_character._12_ABC;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 27). Pearson Education (USA). Kindle Edition.
+ */
+public class Abc {
+    public static void main(String[] args) {
+        String letters = "ABC";
+        char[] numbers = {'1', '2', '3'};
+        System.out.println(letters + " easy as " + numbers);
+
+        // Solution:
+        System.out.println(letters + " easy as ");
+        System.out.println(numbers);
+        // or
+        System.out.println(letters + " easy as " + String.valueOf(numbers));
+    }
+}
+

docs/exPuzzlers/src/_03_character/_13_Animal_Farm/AnimalFarm.java

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+package _03_character._13_Animal_Farm;
+
+/**
+ * Bloch, Joshua; Gafter, Neal (2005-06-24). Java™ Puzzlers: Traps, Pitfalls, and Corner Cases (p. 29). Pearson Education (USA). Kindle Edition.
+ */
+public class AnimalFarm {
+    public static void main(String[] args) {
+        final String pig = "length: 10";
+        final String dog = "length: " + pig.length();
+        System.out.println("Animals are equal: " + pig == dog);
+
+        // Solution:
+        System.out.println("Animals are equal: " + pig.equals(dog));
+        // or
+        System.out.println("Animals are equal: " + (pig.intern() == dog.intern()));
+    }
+}
+

docs/exPuzzlers/src/_03_character/_13_Animal_Farm/AnimalFarm.kt

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+namespace animal.farm
+
+import std.io.*
+import std.*
+
+fun main(args : Array<String>) {
+    val pig = "length: 10";
+    val dog = "length: " + pig.length;
+    println("Animals are equal: " + pig == dog);
+
+    // Solution:
+    println("Animals are equal: " + (pig == dog));
+
+    // Note:
+    println("Animals are equal: " + (pig identityEquals dog));
+}