Fixed random generator

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_01/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_01;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_02/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_02;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_03/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_03;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_04/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_04;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_05/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_05;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_06/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_06;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_07/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_07;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_08/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_08;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/main/java/com/fpinjava/state/exercise12_09/JavaRNG.java

@@ -2,30 +2,33 @@ package com.fpinjava.state.exercise12_09;
 
 import com.fpinjava.common.Tuple;
 
-import java.util.Random;
 
 public class JavaRNG implements RNG {
 
-  private final Random random;
+  private final long seed;
 
   private JavaRNG(long seed) {
-    this.random = new Random(seed);
+    this.seed = seed;
   }
 
   private JavaRNG() {
-    this.random = new Random();
+    this(System.currentTimeMillis());
+  }
+
+  private long nextSeed(long seed) {
+    return (seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1);
   }
 
   @Override
   public Tuple<Integer, RNG> nextInt() {
-    return new Tuple<>(random.nextInt(), this);
+    return new Tuple<>((int)(seed >>> 16), new JavaRNG(nextSeed(seed)));
   }
 
   public static RNG rng(long seed) {
-    return new JavaRNG(seed);
+    return new JavaRNG(seed ^ 0x5DEECE66DL & ((1L << 48) - 1));
   }
 
   public static RNG rng() {
     return new JavaRNG();
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/test/java/com/fpinjava/state/exercise12_01/GeneratorTest.java

 package com.fpinjava.state.exercise12_01;
 
-import com.fpinjava.common.List;
 import com.fpinjava.common.Tuple;
 import org.junit.Test;
 
@@ -12,23 +11,31 @@ public class GeneratorTest {
   public void testInteger() {
     RNG rng = JavaRNG.rng(0);
     Tuple<Integer, RNG> t1 = Generator.integer(rng);
-    assertEquals(Integer.valueOf(-1155484576), t1._1);
+    assertEquals(Integer.valueOf(384748), t1._1);
     Tuple<Integer, RNG> t2 = Generator.integer(t1._2);
-    assertEquals(Integer.valueOf(-723955400), t2._1);
+    assertEquals(Integer.valueOf(-1155484576), t2._1);
     Tuple<Integer, RNG> t3 = Generator.integer(t2._2);
-    assertEquals(Integer.valueOf(1033096058), t3._1);
+    assertEquals(Integer.valueOf(-723955400), t3._1);
     Tuple<Integer, RNG> t4 = Generator.integer(t3._2);
-    assertEquals(Integer.valueOf(-1690734402), t4._1);
+    assertEquals(Integer.valueOf(1033096058), t4._1);
+  }
+
+  @Test
+  public void testIntegerRt() {
+    RNG rng = JavaRNG.rng(0);
+    assertEquals(Integer.valueOf(384748), Generator.integer(rng)._1);
+    assertEquals(Integer.valueOf(384748), Generator.integer(rng)._1);
+    assertEquals(Integer.valueOf(384748), Generator.integer(rng)._1);
   }
 
   @Test
   public void testIntegerLimit() {
     RNG rng = JavaRNG.rng(0);
     Tuple<Integer, RNG> t1 = Generator.integer(rng, 100);
-    assertEquals(Integer.valueOf(76), t1._1);
+    assertEquals(Integer.valueOf(48), t1._1);
     Tuple<Integer, RNG> t2 = Generator.integer(t1._2, 100);
-    assertEquals(Integer.valueOf(0), t2._1);
+    assertEquals(Integer.valueOf(76), t2._1);
     Tuple<Integer, RNG> t3 = Generator.integer(t2._2, 100);
-    assertEquals(Integer.valueOf(58), t3._1);
+    assertEquals(Integer.valueOf(0), t3._1);
   }
 }

fpinjava-parent/fpinjava-state-exercises/src/test/java/com/fpinjava/state/exercise12_02/GeneratorTest.java

@@ -14,18 +14,18 @@ public class GeneratorTest {
   public void testIntegers() {
     RNG rng = JavaRNG.rng(0);
     Tuple<List<Integer>, RNG> result = Generator.integers(rng, 3);
-    assertEquals(List.list(1033096058, -723955400, -1155484576), result._1);
+    assertEquals(List.list(-723955400, -1155484576, 384748), result._1);
     Tuple<Integer, RNG> t = Generator.integer(result._2);
-    assertEquals(Integer.valueOf(-1690734402), t._1);
+    assertEquals(Integer.valueOf(1033096058), t._1);
   }
 
   @Test
   public void testIntegersLength1() {
     RNG rng = JavaRNG.rng(0);
     Tuple<List<Integer>, RNG> result = Generator.integers(rng, 1);
-    assertEquals(List.list(-1155484576), result._1);
+    assertEquals(List.list(384748), result._1);
     Tuple<Integer, RNG> t = Generator.integer(result._2);
-    assertEquals(Integer.valueOf(-723955400), t._1);
+    assertEquals(Integer.valueOf(-1155484576), t._1);
   }
 
   @Test
@@ -34,7 +34,7 @@ public class GeneratorTest {
     Tuple<List<Integer>, RNG> result = Generator.integers(rng, 0);
     assertEquals(0, result._1.length());
     Tuple<Integer, RNG> t = Generator.integer(result._2);
-    assertEquals(Integer.valueOf(-1155484576), t._1);
+    assertEquals(Integer.valueOf(384748), t._1);
   }
 
   @Test
@@ -43,6 +43,6 @@ public class GeneratorTest {
     Tuple<List<Integer>, RNG> result = Generator.integers(rng, -3);
     assertEquals(0, result._1.length());
     Tuple<Integer, RNG> t = Generator.integer(result._2);
-    assertEquals(Integer.valueOf(-1155484576), t._1);
+    assertEquals(Integer.valueOf(384748), t._1);
   }
 }

fpinjava-parent/fpinjava-state-exercises/src/test/java/com/fpinjava/state/exercise12_04/RandomTest.java

@@ -12,10 +12,10 @@ public class RandomTest {
   public void testDoubleRnd() throws Exception {
     RNG rng = JavaRNG.rng(0);
     Tuple<Double, RNG> result1 = Random.doubleRnd.apply(rng);
-    assertTrue(Math.abs(-0.5380644351243973 - result1._1) < 0.0001);
+    assertTrue(Math.abs(1.7916224896907806E-4 - result1._1) < 0.0001);
     Tuple<Double, RNG> result2 = Random.doubleRnd.apply(result1._2);
-    assertTrue(Math.abs(-0.3371180035173893 - result2._1) < 0.0001);
+    assertTrue(Math.abs(-0.5380644351243973 - result2._1) < 0.0001);
     Tuple<Double, RNG> result3 = Random.doubleRnd.apply(result2._2);
-    assertTrue(Math.abs(0.48107284028083086 - result3._1) < 0.0001);
+    assertTrue(Math.abs(-0.3371180035173893 - result3._1) < 0.0001);
   }
-}
+}
\ No newline at end of file

fpinjava-parent/fpinjava-state-exercises/src/test/java/com/fpinjava/state/exercise12_05/RandomTest.java

 package com.fpinjava.state.exercise12_05;
 
-import org.junit.Test;
-
 import static org.junit.Assert.*;
 
 import com.fpinjava.common.Tuple;
@@ -16,9 +14,9 @@ public class RandomTest {
   public void testMap2() {
     RNG rng = JavaRNG.rng(0);
     Tuple<Tuple<Integer, Integer>, RNG> result = Random.intPairRnd.apply(rng);
-    assertEquals(Integer.valueOf(-1155484576), result._1._1);
-    assertEquals(Integer.valueOf(-723955400), result._1._2);
+    assertEquals(Integer.valueOf(384748), result._1._1);
+    assertEquals(Integer.valueOf(-1155484576), result._1._2);
     Tuple<Integer, RNG> t = Random.intRnd.apply(result._2);
-    assertEquals(Integer.valueOf(1033096058), t._1);
+    assertEquals(Integer.valueOf(-723955400), t._1);
   }
 }

fpinjava-parent/fpinjava-state-exercises/src/test/java/com/fpinjava/state/exercise12_06/RandomTest.java

@@ -17,18 +17,18 @@ public class RandomTest {
   public void testSequence() {
     RNG rng = JavaRNG.rng(0);
     Tuple<List<Integer>, RNG> result = Random.integersRnd.apply(3).apply(rng);
-    assertEquals(List.list(-1155484576, -723955400, 1033096058), result._1);
+    assertEquals(List.list(384748, -1155484576, -723955400), result._1);
     Tuple<Integer, RNG> t = Random.intRnd.apply(result._2);
-    assertEquals(Integer.valueOf(-1690734402), t._1);
+    assertEquals(Integer.valueOf(1033096058), t._1);
   }
 
   @Test
   public void testSequenceLength1() {
     RNG rng = JavaRNG.rng(0);
     Tuple<List<Integer>, RNG> result = Random.integersRnd.apply(1).apply(rng);
-    assertEquals(List.list(-1155484576), result._1);
+    assertEquals(List.list(384748), result._1);
     Tuple<Integer, RNG> t = Random.intRnd.apply(result._2);
-    assertEquals(Integer.valueOf(-723955400), t._1);
+    assertEquals(Integer.valueOf(-1155484576), t._1);
   }
 
   @Test
@@ -37,7 +37,7 @@ public class RandomTest {
     Tuple<List<Integer>, RNG> result = Random.integersRnd.apply(0).apply(rng);
     assertEquals(0, result._1.length());
     Tuple<Integer, RNG> t = Random.intRnd.apply(result._2);
-    assertEquals(Integer.valueOf(-1155484576), t._1);
+    assertEquals(Integer.valueOf(384748), t._1);
   }
 
   @Test
@@ -46,6 +46,6 @@ public class RandomTest {
     Tuple<List<Integer>, RNG> result = Random.integersRnd.apply(-3).apply(rng);
     assertEquals(0, result._1.length());
     Tuple<Integer, RNG> t = Random.intRnd.apply(result._2);
-    assertEquals(Integer.valueOf(-1155484576), t._1);
+    assertEquals(Integer.valueOf(384748), t._1);