56 - Using Custom Objects in Sets and as Keys in Maps

56 - Using Custom Objects in Sets and as Keys in Maps/src/App.java

@@ -0,0 +1,81 @@
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.Map;
+import java.util.Set;
+
+class Person {
+    private int id;
+    private String name;
+
+    public Person(int id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public String toString() {
+        return "{ID is: " + id + "; name is: " + name + "}";
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + id;
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        final Person other = (Person) obj;
+        if (id != other.id)
+            return false;
+        if (name == null) {
+            if (other.name != null)
+                return false;
+        } else if (!name.equals(other.name))
+            return false;
+        return true;
+    }
+
+
+}
+
+
+public class App {
+
+    public static void main(String[] args) {
+
+        Person p1 = new Person(0, "Bob");
+        Person p2 = new Person(1, "Sue");
+        Person p3 = new Person(2, "Mike");
+        Person p4 = new Person(1, "Sue");
+
+        Map<Person, Integer> map = new LinkedHashMap<Person, Integer>();
+
+        map.put(p1, 1);
+        map.put(p2, 2);
+        map.put(p3, 3);
+        map.put(p4, 1);
+
+        for(Person key: map.keySet()) {
+            System.out.println(key + ": " + map.get(key));
+        }
+
+        Set<Person> set = new LinkedHashSet<Person>();
+
+        set.add(p1);
+        set.add(p2);
+        set.add(p3);
+        set.add(p4);
+
+        System.out.println(set);
+    }
+
+}