interface Pair<T1, T2> { T1 getFirst(); T2 getSecond(); }

Week 7: Enum, Generic Type, Streams, write to file, class diagram/06A. Generics in Interface Classes++

@@ -0,0 +1,77 @@
+A 'generic type' can also be defined for an 'interface class', for example:
+
+interface Pair<T1, T2> {
+    T1 getFirst();
+    T2 getSecond();
+}
+ 
+
+Now the types can either be fixed when writing the class implementing the interface…
+ 
+class StudentPair implements Pair<Student, Student> {
+
+    private Student s1;
+    private Student s2;
+    
+    public StudentPair(Student s1, Student s2) {
+        this.s1 = s1;
+        this.s2 = s2;
+    }
+    
+    @Override
+    public Student getFirst() {
+        return s1;
+    }
+
+    @Override
+    public Student getSecond() {
+        return s2;
+    }  
+}
+
+
+
+
+
+
+...or also write the implementing class 'generically typed', 
+in which case the type is given only when an object is created from the class:
+
+class Tuple<T1, T2> implements Pair<T1, T2> {
+    
+    private T1 first;
+    private T2 second;
+    
+    public Tuple(T1 first, T2 second) {
+        this.first = first;
+        this.second = second;
+    }
+
+    @Override
+    public T1 getFirst() {
+        return first;
+    }
+
+    @Override
+    public T2 getSecond() {
+        return second;
+    }
+}
+
+
+ 
+
+Example of using the class:
+public static void main(String[] args) {
+    Tuple<Integer, Double> numbers = new Tuple<>(10, 0.25);
+    System.out.println(numbers.getFirst());
+    System.out.println(numbers.getSecond());
+}
+ 
+
+The program prints:
+10
+0.25
+
+
+