Day 3 break 3

Questions.txt

@@ -630,3 +630,35 @@ B) Consumer<String> cs = s -> { System.out.println(s); };
 C) Supplier<String> ss = (s1, s2) -> s1 + s2;
 D) BiPredicate<String> bps = (String s) -> { return s.length() > 0; };
 E) ToIntFunction<String> tofs = s -> s.length();
+
+Q) Given:
+      ???? (s, t) -> s.length() - t.length();
+
+Which are correct inserted in place of ????
+A) BiFunction<String, String, Integer> f =
+B) BiPredicate<String> f =
+C) Comparator<String> f =
+D) Supplier<String, Integer> f =
+E) BinaryOperator<String> f =
+
+Q) Given, in a single file X.java:
+interface ArbInter {}
+final class Y implements X {}
+sealed interface X /* point x */{}
+// line n1
+
+Which is/are true?
+A) the code compiles as it stands
+B) the code compiles if the following is added at point x
+permits Y, Z
+AND this is added at line 1
+class Z implements X {}
+C) the code compiles if the following is added at point x
+permits Y, Z
+AND this is added at line 1
+record Z(String name) implements X {}
+D) the code compiles if the following is added at point x
+   permits Y extends ArbInter
+E) the code compiles if the following is added at line n1
+non-sealed abstract class Z implements X permits Q {}
+final class Q extends Z {}

src/main/java/doublestuff/Parsing.java

@@ -0,0 +1,10 @@
+package doublestuff;
+
+public class Parsing {
+  public static void main(String[] args) {
+    System.out.println(Double.parseDouble("Infinity"));
+    System.out.println(Double.parseDouble("-Infinity"));
+    System.out.println(Double.parseDouble("+Infinity"));
+    System.out.println(Double.parseDouble("NaN"));
+  }
+}

src/main/java/lambdas/Demos.java

@@ -1,15 +1,21 @@
 package lambdas;
 
+import java.util.Comparator;
 import java.util.List;
-import java.util.function.ToIntFunction;
+import java.util.function.*;
 
 interface StudentCriterion {
   boolean test(Student s);
 }
 
 class Student {
-  public int getGpa() { return 0; }
-  public List<String> getCourses() { return null; }
+  public int getGpa() {
+    return 0;
+  }
+
+  public List<String> getCourses() {
+    return null;
+  }
 }
 
 class SmartStudent implements StudentCriterion {
@@ -72,5 +78,37 @@ public static void main(String[] args) {
 //    Long lng = 99; // Nope
     Byte b = null;
     long lng = b;
+
+    Object BiPredicate;
+//    BiFunction<String, String, Integer> f = (s, t) -> s.length() - t.length();
+//    BiPredicate<String> f = (s, t) -> s.length() - t.length();
+//    Comparator<String> f = (s, t) -> s.length() - t.length();
+//    Supplier<String, Integer> f = (s, t) -> s.length() - t.length();
+    BinaryOperator<String> f = (s, t) -> (s.length() - t.length()) + "";
+//    BinaryOperator<String> f = (s, t) -> s + t;
+
+//    IntFunction<Integer> f1 = (f) -> f;
+//    f1.applyAsInt(Integer.valueOf(0));
+  }
+
+  interface BiFunction<A1, A2, R> {
+    R apply(A1 a1, A2 a2);
+  }
+
+  interface IntFunction<E> {
+    E applyAsInt(int i);
+  }
+  class MyIntFunction implements IntFunction<Integer> {
+    @Override
+//    public Integer applyAsInt(Integer f) {
+    public Integer applyAsInt(int f) {
+//      return Integer.valueOf(f);
+      return f;
+    }
+    @Override
+//    public boolean equals(MyIntFunction me) { return false; }
+    public boolean equals(Object me) { return false; }
+
+
   }
 }

src/main/java/sealedtypes/Ex1.java

@@ -0,0 +1,25 @@
+package sealedtypes;
+
+interface Transporter {
+}
+
+class Truck implements Transporter {
+}
+
+class Car implements Transporter {
+}
+
+//class Bicycle implements Transporter {}
+
+public class Ex1 {
+  public static void main(String[] args) {
+    Transporter t = Math.random() > 0.5 ? new Truck() : new Car();
+
+    if (t instanceof Truck tr) {
+      // can the truck do this?
+    } else if (t instanceof Car c) {
+      // can the car do this?
+    }
+
+  }
+}