6 files changed, 75 insertions, 0 deletions
diff --git a/Year_2/SE/L21_ex2/Main.java b/Year_2/SE/L21_ex2/Main.java
new file mode 100644
index 0000000..6f077f9
--- /dev/null
+++ b/Year_2/SE/L21_ex2/Main.java
@@ -0,0 +1,11 @@
+import java.util.List;
+
+public class Main {
+    public static void main(String[] args) {
+        List<String> l = List.of("to", "speak", "the", "truth", "and", "pay", "your", "debts");
+        l.stream()
+            .map(x -> x.charAt(0))
+            .forEach(c -> System.out.print(c));
+    }
+}
+
diff --git a/Year_2/SE/design_patterns/singleton/Logs.java b/Year_2/SE/design_patterns/singleton/Logs.java
new file mode 100644
index 0000000..85deef9
--- /dev/null
+++ b/Year_2/SE/design_patterns/singleton/Logs.java
@@ -0,0 +1,10 @@
+public class Logs {
+    private static Logs log;
+
+    private Logs(){}
+
+    public static Logs getInstanceLogs() {
+        if(log == null) log = new Logs();
+        return log;
+    }
+}
diff --git a/Year_2/SE/design_patterns/singleton/Main.java b/Year_2/SE/design_patterns/singleton/Main.java
new file mode 100644
index 0000000..5d05cea
--- /dev/null
+++ b/Year_2/SE/design_patterns/singleton/Main.java
@@ -0,0 +1,12 @@
+public class Main {
+    public static void main(String[] args) {
+        Logs l = Logs.getInstanceLogs();
+        Logs l2 = Logs.getInstanceLogs();
+
+        // Prints "true"
+        System.out.println(l == l2);
+
+        // Error, because the constructor is private
+        // Logs l3 = new Logs();
+    }
+}
diff --git a/Year_2/SE/error_inheritance/Main.java b/Year_2/SE/error_inheritance/Main.java
new file mode 100644
index 0000000..206a513
--- /dev/null
+++ b/Year_2/SE/error_inheritance/Main.java
@@ -0,0 +1,19 @@
+public class Main {
+    public static void main(String[] args) {
+        Student s = new Student();
+        s.setName("Santo");
+        s.setMatr("1948");
+
+        s.print();
+
+        Person p = s;
+        // That's not compile
+        // p.setMatr("1949");
+        p.setName("John");
+        p.print();
+
+        // s.name is equals to p.name, so the code below print
+        // Hello, John[...]
+        s.print();
+    }
+}
diff --git a/Year_2/SE/error_inheritance/Person.java b/Year_2/SE/error_inheritance/Person.java
new file mode 100644
index 0000000..2e52d79
--- /dev/null
+++ b/Year_2/SE/error_inheritance/Person.java
@@ -0,0 +1,10 @@
+public class Person {
+    private String name;
+    public void setName(String n) {
+        this.name = n;
+    }
+
+    public void print() {
+        System.out.println("Hello, "+ this.name);
+    }
+}
diff --git a/Year_2/SE/error_inheritance/Student.java b/Year_2/SE/error_inheritance/Student.java
new file mode 100644
index 0000000..1789489
--- /dev/null
+++ b/Year_2/SE/error_inheritance/Student.java
@@ -0,0 +1,13 @@
+public class Student extends Person {
+    private String matr;
+
+    public void setMatr(String m) {
+        this.matr = m;
+    }
+
+    @Override
+    public void print() {
+        super.print();
+        System.out.println("I'm "+ this.matr);
+    }
+}