Initial Commit (#2349)

core-java/src/main/java/com/baeldung/hashcode/application/Application.java

@@ -0,0 +1,23 @@
+package com.baeldung.application;
+
+import com.baeldung.entities.User;
+import java.util.HashMap;
+import java.util.Map;
+
+public class Application {
+
+    public static void main(String[] args) {
+        Map<User, User> users = new HashMap<>();
+        User user1 = new User(1L, "John", "john@domain.com");
+        User user2 = new User(2L, "Jennifer", "jennifer@domain.com");
+        User user3 = new User(3L, "Mary", "mary@domain.com");
+
+        users.put(user1, user1);
+        users.put(user2, user2);
+        users.put(user3, user3);
+
+        if (users.containsKey(user1)) {
+            System.out.print("User found in the collection");
+        }
+    }
+}

core-java/src/main/java/com/baeldung/hashcode/entities/User.java

@@ -0,0 +1,38 @@
+package com.baeldung.entities;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class User {
+
+    private final Logger logger = LoggerFactory.getLogger(User.class);
+    private long id;
+    private String name;
+    private String email;
+
+    public User(long id, String name, String email) {
+        this.id = id;
+        this.name = name;
+        this.email = email;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null) return false;
+        if (this.getClass() != o.getClass()) return false;
+        User user = (User) o;
+        return id != user.id && (!name.equals(user.name) && !email.equals(user.email));
+    }
+    	
+    @Override
+    public int hashCode() {
+        int hash = 7;
+        hash = 31 * hash + (int) id;
+        hash = 31 * hash + (name == null ? 0 : name.hashCode());
+        hash = 31 * hash + (email == null ? 0 : email.hashCode());
+        logger.info("hashCode() method called - Computed hash: " + hash);
+        return hash;
+    }
+    // getters and setters here
+}