Add some examples

JavaExamples.java

@@ -0,0 +1,93 @@
+/// Java Examples
+import java.util.*;
+import qual.Immutable;
+import qual.Mutable;
+
+public class JavaExamples {
+    // Mutating immut set, `s` is immut
+    void foo(@Immutable Set<String> s) {
+        Set<String> new_s = s; // Flow sensitive will refine this to @Immutable
+        @Mutable Set<String> new_s1 = s; // ERROR, type incompatible
+        new_s.add("x"); // ERROR
+    }
+
+    // Mutating immut set, `new_s` is immut
+    void foo1(@Mutable Set<String> s) {
+        @Immutable Set<String> new_s = new @Immutable HashSet<>(s);
+        Set<String> new_s1 = s; // Flow sensitive will refine this to @Mutable
+        new_s.add("x"); // ERROR
+        new_s1.add("x"); //OK
+    }
+
+    // Mutating mut set
+    void foo2(Set<String> s) {
+        @Mutable Set<String> new_s = new HashSet<>(s);
+        new_s.add("x"); // OK
+    }
+
+    void foo3(List<@Immutable List<String>> s, int l) {
+        List<String> v = s.get(l);
+        @Mutable List<String> v2 = s.get(l); // ERROR
+        v.add("x"); // ERROR
+    }
+
+    void foo4(Person p) {
+        p.name = "Jenny"; // Ok, this should be forbid by compiler by adding final before String
+        p.family.add("Jenny"); // ERROR, can not mutate immut list
+    }
+
+    void foo5(MutPerson p) {
+        p.name = "Jenny"; // OK
+        p.family.add("Jenny"); // OK
+        p.getFamily().add("Jenny"); // OK
+    }
+}
+
+// Class and its immut members
+class Person {
+    String name; // String is default @Immutable, use final to prevent reassignment
+    @Immutable List<String> family;
+
+    Person(String n, @Immutable List<String> f) {
+        this.name = n; // OK
+        this.family = f; // OK
+        this.family.add("Mom"); // ERROR
+    }
+
+    void setName(String n) {
+        this.name = n; // Ok, this should be forbid by compiler by adding final before String
+    }
+
+    @Mutable List<String> getFamily() {
+        return family; // ERROR, type incompatible
+    }
+}
+
+// Class and its mut members
+class MutPerson {
+    String name; // String is default @Immutable in PICO
+    @Mutable List<String> family;
+
+    MutPerson(String n, List<String> f) {
+        this.name = n; // OK
+        this.family = f; // OK
+        this.family.add("Mom"); // OK
+    }
+
+    void setName(String n) {
+        this.name = n; // OK
+    }
+
+    List<String> getFamily() {
+        return family; // OK
+    }
+}
+
+class ImmutSet<T> {
+    void foo1 (ImmutSet<MutList<T>> s) {  // ERROR
+    }
+    void foo2(MutList<ImmutSet<T>> s) {  // OK
+    }
+}
+
+@Mutable class MutList<@Mutable T> {}