[rajkishorraj185@gmail.com] Lombok equalsandhashcode annotation (#13717)

* example code for equalsandhashcode annotation

* moving codes to lombok-2

---------

Co-authored-by: raj kishor <raj.kishor@smartcoin.co.in>

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/Employee.java

@@ -0,0 +1,14 @@
+package com.baeldung.lombok.equalsandhashcode;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+
+@Getter
+@EqualsAndHashCode
+@AllArgsConstructor
+public class Employee {
+    private String name;
+    private int id;
+    private int age;
+}

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/EmployeeDelomboked.java

@@ -0,0 +1,57 @@
+package com.baeldung.lombok.equalsandhashcode;
+
+import lombok.Getter;
+
+@Getter
+public class EmployeeDelomboked {
+
+    private String name;
+    private int id;
+    private int age;
+
+    public EmployeeDelomboked() {
+    }
+
+    public boolean equals(Object o) {
+        if (o == this) {
+            return true;
+        } else if (!(o instanceof Employee)) {
+            return false;
+        } else {
+            Employee other = (Employee) o;
+            if (!other.canEqual(this)) {
+                return false;
+            } else if (this.getId() != other.getId()) {
+                return false;
+            } else if (this.getAge() != other.getAge()) {
+                return false;
+            } else {
+                Object this$name = this.getName();
+                Object other$name = other.getName();
+                if (this$name == null) {
+                    if (other$name == null) {
+                        return true;
+                    }
+                } else if (this$name.equals(other$name)) {
+                    return true;
+                }
+
+                return false;
+            }
+        }
+    }
+
+    protected boolean canEqual(Object other) {
+        return other instanceof Employee;
+    }
+
+    public int hashCode() {
+        final int PRIME = 59;
+        int result = 1;
+        result = result * PRIME + this.getId();
+        result = result * PRIME + this.getAge();
+        Object $name = this.getName();
+        result = result * PRIME + ($name == null ? 43 : $name.hashCode());
+        return result;
+    }
+}

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/commonissue/Employee.java

@@ -0,0 +1,20 @@
+package com.baeldung.lombok.equalsandhashcode.commonissue;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+
+@Getter
+@Setter
+@EqualsAndHashCode
+@AllArgsConstructor
+@NoArgsConstructor
+public class Employee {
+    private String name;
+    private int id;
+    private int age;
+    private Manager manager;
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/commonissue/EmployeeV2.java

@@ -0,0 +1,17 @@
+package com.baeldung.lombok.equalsandhashcode.commonissue;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+@EqualsAndHashCode(exclude = "manager")
+@AllArgsConstructor
+public class EmployeeV2 {
+    private String name;
+    private int id;
+    private int age;
+    private ManagerV2 manager;
+}

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/commonissue/Manager.java

@@ -0,0 +1,16 @@
+package com.baeldung.lombok.equalsandhashcode.commonissue;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+@EqualsAndHashCode
+@AllArgsConstructor
+public class Manager {
+    private String name;
+    private Employee assistantManager;
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/commonissue/ManagerV2.java

@@ -0,0 +1,16 @@
+package com.baeldung.lombok.equalsandhashcode.commonissue;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+@EqualsAndHashCode
+@AllArgsConstructor
+public class ManagerV2 {
+    private String name;
+    private EmployeeV2 assistantManager;
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/exclude/classlevel/Employee.java

@@ -0,0 +1,15 @@
+package com.baeldung.lombok.equalsandhashcode.exclude.classlevel;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+
+@Getter
+@EqualsAndHashCode(exclude = {"id", "age"})
+@AllArgsConstructor
+public class Employee {
+    private String name;
+    private int id;
+    private int age;
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/exclude/classlevel/EmployeeDelomboked.java

@@ -0,0 +1,37 @@
+package com.baeldung.lombok.equalsandhashcode.exclude.classlevel;
+
+
+import lombok.Getter;
+
+@Getter
+public class EmployeeDelomboked {
+    private String name;
+    private int id;
+    private int age;
+
+    @Override
+    public boolean equals(final Object o) {
+        if (o == this) return true;
+        if (!(o instanceof Employee)) return false;
+        final Employee other = (Employee) o;
+        if (!other.canEqual((Object) this)) return false;
+        final Object this$name = this.getName();
+        final Object other$name = other.getName();
+        if (this$name == null ? other$name != null : !this$name.equals(other$name)) return false;
+        return true;
+    }
+
+    protected boolean canEqual(final Object other) {
+        return other instanceof Employee;
+    }
+
+    @Override
+    public int hashCode() {
+        final int PRIME = 59;
+        int result = 1;
+        final Object $name = this.getName();
+        result = result * PRIME + ($name == null ? 43 : $name.hashCode());
+        return result;
+    }
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/exclude/fieldlevel/Employee.java

@@ -0,0 +1,18 @@
+package com.baeldung.lombok.equalsandhashcode.exclude.fieldlevel;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+
+@Getter
+@EqualsAndHashCode
+@AllArgsConstructor
+public class Employee {
+    private String name;
+    @EqualsAndHashCode.Exclude
+    private int id;
+    @EqualsAndHashCode.Exclude
+    private int age;
+}
+
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/exclude/fieldlevel/EmployeeDelomboked.java

@@ -0,0 +1,31 @@
+package com.baeldung.lombok.equalsandhashcode.exclude.fieldlevel;
+
+
+import lombok.Getter;
+
+@Getter
+public class EmployeeDelomboked {
+    private String name;
+    private int id;
+    private int age;
+
+    public boolean equals(final Object o) {
+        if (o == this) return true;
+        if (!(o instanceof com.baeldung.lombok.equalsandhashcode.exclude.fieldlevel.Employee)) return false;
+        final com.baeldung.lombok.equalsandhashcode.exclude.fieldlevel.Employee other = (com.baeldung.lombok.equalsandhashcode.exclude.fieldlevel.Employee) o;
+        if (!other.canEqual((Object) this)) return false;
+        final Object this$name = this.getName();
+        final Object other$name = other.getName();
+        if (this$name == null ? other$name != null : !this$name.equals(other$name)) return false;
+        return true;
+    }
+
+    public int hashCode() {
+        final int PRIME = 59;
+        int result = 1;
+        final Object $name = this.getName();
+        result = result * PRIME + ($name == null ? 43 : $name.hashCode());
+        return result;
+    }
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/include/classlevel/Employee.java

@@ -0,0 +1,15 @@
+package com.baeldung.lombok.equalsandhashcode.include.classlevel;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+
+@Data
+@EqualsAndHashCode(of = {"name", "id"})
+@AllArgsConstructor
+public class Employee {
+    private String name;
+    private int id;
+    private int age;
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/include/fieldlevel/Employee.java

@@ -0,0 +1,18 @@
+package com.baeldung.lombok.equalsandhashcode.include.fieldlevel;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+
+@Getter
+@EqualsAndHashCode(onlyExplicitlyIncluded = true)
+@AllArgsConstructor
+public class Employee {
+    @EqualsAndHashCode.Include
+    private String name;
+    @EqualsAndHashCode.Include
+    private int id;
+    private int age;
+}
+
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/include/methodlevel/Employee.java

@@ -0,0 +1,20 @@
+package com.baeldung.lombok.equalsandhashcode.include.methodlevel;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+
+@Getter
+@EqualsAndHashCode
+@AllArgsConstructor
+public class Employee {
+    private String name;
+    private int id;
+    private int age;
+
+    @EqualsAndHashCode.Include
+    public boolean hasOddId() {
+        return id % 2 != 0;
+    }
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/include/methodlevel/EmployeeDelomboked.java

@@ -0,0 +1,40 @@
+package com.baeldung.lombok.equalsandhashcode.include.methodlevel;
+
+import lombok.Getter;
+
+@Getter
+public class EmployeeDelomboked {
+    private String name;
+    private int id;
+    private int age;
+
+    public boolean hasOddId() {
+        return id % 2 != 0;
+    }
+
+    public boolean equals(final Object o) {
+        if (o == this) return true;
+        if (!(o instanceof Employee)) return false;
+        final Employee other = (Employee) o;
+        if (!other.canEqual((Object) this)) return false;
+        if (this.getId() != other.getId()) return false;
+        if (this.getAge() != other.getAge()) return false;
+        if (this.hasOddId() != other.hasOddId()) return false;
+        final Object this$name = this.getName();
+        final Object other$name = other.getName();
+        if (this$name == null ? other$name != null : !this$name.equals(other$name)) return false;
+        return true;
+    }
+
+    public int hashCode() {
+        final int PRIME = 59;
+        int result = 1;
+        result = result * PRIME + this.getId();
+        result = result * PRIME + this.getAge();
+        result = result * PRIME + (this.hasOddId() ? 79 : 97);
+        final Object $name = this.getName();
+        result = result * PRIME + ($name == null ? 43 : $name.hashCode());
+        return result;
+    }
+}
+

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/inheritance/Employee.java

@@ -0,0 +1,16 @@
+package com.baeldung.lombok.equalsandhashcode.inheritance;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+@EqualsAndHashCode
+@AllArgsConstructor
+public class Employee {
+    private String name;
+    private int id;
+    private int age;
+}

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/inheritance/Manager.java

@@ -0,0 +1,20 @@
+package com.baeldung.lombok.equalsandhashcode.inheritance;
+
+import lombok.AllArgsConstructor;
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+@EqualsAndHashCode(callSuper = true)
+public class Manager extends Employee {
+    private String departmentName;
+    private int uid;
+
+    public Manager(String departmentName, int uid, String name, int id, int age) {
+        super(name, id, age);
+        this.departmentName = departmentName;
+        this.uid = uid;
+    }
+}

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/inheritance/ManagerDelomboked.java

@@ -0,0 +1,37 @@
+package com.baeldung.lombok.equalsandhashcode.inheritance;
+
+import lombok.Getter;
+
+@Getter
+public class ManagerDelomboked extends Employee {
+    private String departmentName;
+    private int uid;
+
+    public ManagerDelomboked(String departmentName, int uid, String name, int id, int age) {
+        super(name, id, age);
+        this.departmentName = departmentName;
+        this.uid = uid;
+    }
+
+    public boolean equals(final Object o) {
+        if (o == this) return true;
+        if (!(o instanceof com.baeldung.lombok.equalsandhashcode.inheritance.Manager)) return false;
+        final com.baeldung.lombok.equalsandhashcode.inheritance.Manager other = (com.baeldung.lombok.equalsandhashcode.inheritance.Manager) o;
+        if (!other.canEqual((Object) this)) return false;
+        if (!super.equals(o)) return false;
+        if (this.getUid() != other.getUid()) return false;
+        final Object this$departmentName = this.getDepartmentName();
+        final Object other$departmentName = other.getDepartmentName();
+        if (this$departmentName == null ? other$departmentName != null : !this$departmentName.equals(other$departmentName)) return false;
+        return true;
+    }
+
+    public int hashCode() {
+        final int PRIME = 59;
+        int result = super.hashCode();
+        result = result * PRIME + this.getUid();
+        final Object $departmentName = this.getDepartmentName();
+        result = result * PRIME + ($departmentName == null ? 43 : $departmentName.hashCode());
+        return result;
+    }
+}

lombok-modules/lombok-2/src/main/java/com/baeldung/lombok/equalsandhashcode/inheritance/ManagerV2.java

@@ -0,0 +1,19 @@
+package com.baeldung.lombok.equalsandhashcode.inheritance;
+
+import lombok.EqualsAndHashCode;
+import lombok.Getter;
+import lombok.Setter;
+
+@Getter
+@Setter
+@EqualsAndHashCode(callSuper = false)
+public class ManagerV2 extends Employee {
+    private String departmentName;
+    private int uid;
+
+    public ManagerV2(String departmentName, int uid, String name, int id, int age) {
+        super(name, id, age);
+        this.departmentName = departmentName;
+        this.uid = uid;
+    }
+}

lombok-modules/lombok-2/src/test/java/com/baeldung/lombok/equalsandhashcode/EqualsAndHashCodeUnitTest.java

@@ -0,0 +1,20 @@
+package com.baeldung.lombok.equalsandhashcode;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class EqualsAndHashCodeUnitTest {
+
+    @Test
+    public void whenUsingEqualsAndHashCodeOnClassLevel_thenTwoObjectsAreEqualAndHaveSameHashCodeIfAllFieldsAreSame() {
+        Employee employee = new Employee("Nimi", 15, 22);
+        Employee employeeTwo = new Employee("Nimi", 15, 22);
+        Employee employeeThree = new Employee("Mannat", 15, 22);
+        assertEquals(employee, employeeTwo);
+        assertNotEquals(employee, employeeThree);
+        assertEquals(employee.hashCode(), employeeTwo.hashCode());
+        assertNotEquals(employee.hashCode(), employeeThree.hashCode());
+    }
+}

lombok-modules/lombok-2/src/test/java/com/baeldung/lombok/equalsandhashcode/commonissue/EqualsAndHashCodeUnitTest.java

@@ -0,0 +1,34 @@
+package com.baeldung.lombok.equalsandhashcode.commonissue;
+
+import org.junit.Test;
+
+public class EqualsAndHashCodeUnitTest {
+
+    @Test(expected = StackOverflowError.class)
+    public void whenUsingEqualsAndHashInObjectWithCircularDependency_thenCallingEqualsAndHasCodeWillThrowStackOverFlowError() {
+        Manager manager = new Manager("Mannat", null);
+
+        Employee employee = new Employee("Nimi", 15, 22, manager);
+
+        manager.setAssistantManager(employee);
+
+        employee.setManager(manager);
+
+        int hash = employee.hashCode();
+
+    }
+
+    @Test
+    public void whenUsingEqualsAndHashInObjectAndExcludingCircularDependencyField_thenNoStackOverFlowError() {
+        ManagerV2 manager = new ManagerV2("Mannat", null);
+
+        EmployeeV2 employee = new EmployeeV2("Nimi", 15, 22, manager);
+
+        manager.setAssistantManager(employee);
+
+        employee.setManager(manager);
+
+        int hash = employee.hashCode();
+
+    }
+}

lombok-modules/lombok-2/src/test/java/com/baeldung/lombok/equalsandhashcode/exclude/classlevel/EqualsAndHashCodeUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.lombok.equalsandhashcode.exclude.classlevel;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class EqualsAndHashCodeUnitTest {
+
+    @Test
+    public void whenUsingEqualsAndHashCodeOnClassLevelAndExcludingFields_thenTwoObjectsAreEqualAndHaveSameHashCodeEvenIfExcludedFieldsAreNotSame() {
+        Employee employee = new Employee("Nimi", 15, 22);
+        Employee employeeTwo = new Employee("Nimi", 17, 21);
+
+        assertEquals(employee, employeeTwo);
+        assertEquals(employee.hashCode(), employeeTwo.hashCode());
+    }
+}

lombok-modules/lombok-2/src/test/java/com/baeldung/lombok/equalsandhashcode/exclude/fieldLevel/EqualsAndHashCodeUnitTest.java

@@ -0,0 +1,18 @@
+package com.baeldung.lombok.equalsandhashcode.exclude.fieldLevel;
+
+import com.baeldung.lombok.equalsandhashcode.exclude.fieldlevel.Employee;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class EqualsAndHashCodeUnitTest {
+
+    @Test
+    public void whenUsingEqualsAndHashCodeWithExcludingFields_thenTwoObjectsAreEqualAndHaveSameHashCodeEvenIfExcludedFieldsAreNotSame() {
+        Employee employee = new Employee("Nimi", 15, 22);
+        Employee employeeTwo = new Employee("Nimi", 17, 21);
+
+        assertEquals(employee, employeeTwo);
+        assertEquals(employee.hashCode(), employeeTwo.hashCode());
+    }
+}

lombok-modules/lombok-2/src/test/java/com/baeldung/lombok/equalsandhashcode/include/classlevel/EqualsAndHashCodeUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.lombok.equalsandhashcode.include.classlevel;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class EqualsAndHashCodeUnitTest {
+
+    @Test
+    public void whenUsingEqualsAndHashCodeOnClassLevelAndIncludeFields_thenTwoObjectsAreEqualAndHaveSameHashCodeIfIncludedFieldsAreSame() {
+        Employee employee = new Employee("Nimi", 15, 22);
+        Employee employeeTwo = new Employee("Nimi", 15, 22);
+        Employee employeeThree = new Employee("Nimi", 15, 23);
+
+        assertEquals(employee, employeeTwo);
+        assertEquals(employee, employeeThree);
+
+        assertEquals(employee.hashCode(), employeeTwo.hashCode());
+        assertEquals(employee.hashCode(), employeeThree.hashCode());
+    }
+}

lombok-modules/lombok-2/src/test/java/com/baeldung/lombok/equalsandhashcode/include/fieldlevel/EqualsAndHashCodeUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.lombok.equalsandhashcode.include.fieldlevel;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class EqualsAndHashCodeUnitTest {
+
+    @Test
+    public void whenUsingEqualsAndHashCodeOnFieldLevel_thenTwoObjectsAreEqualAndHaveSameHashCodeIfIncludedFieldsAreSame() {
+        Employee employee = new Employee("Nimi", 15, 22);
+        Employee employeeTwo = new Employee("Nimi", 15, 22);
+        Employee employeeThree = new Employee("Nimi", 15, 23);
+
+        assertEquals(employee, employeeTwo);
+        assertEquals(employee, employeeThree);
+
+        assertEquals(employee.hashCode(), employeeTwo.hashCode());
+        assertEquals(employee.hashCode(), employeeThree.hashCode());
+    }
+}

lombok-modules/lombok-2/src/test/java/com/baeldung/lombok/equalsandhashcode/include/methodlevel/EqualsAndHashCodeUnitTest.java

@@ -0,0 +1,22 @@
+package com.baeldung.lombok.equalsandhashcode.include.methodlevel;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class EqualsAndHashCodeUnitTest {
+
+    @Test
+    public void whenUsingEqualsAndHashCodeOnMethodLevel_thenTwoObjectsAreEqualAndHaveSameHashCodeIfMethodsReturnSameValue() {
+        Employee employee = new Employee("Nimi", 15, 22);
+        Employee employeeTwo = new Employee("Nimi", 15, 22);
+        Employee employeeThree = new Employee("Nimi", 15, 23);
+
+        assertEquals(employee, employeeTwo);
+        assertNotEquals(employee, employeeThree);
+
+        assertEquals(employee.hashCode(), employeeTwo.hashCode());
+        assertNotEquals(employee.hashCode(), employeeThree.hashCode());
+    }
+}

lombok-modules/lombok-2/src/test/java/com/baeldung/lombok/equalsandhashcode/inheritance/EqualsAndHashCodeUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.lombok.equalsandhashcode.inheritance;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class EqualsAndHashCodeUnitTest {
+
+    @Test
+    public void whenUsingEqualsAndHashCodeAndCallSuperIsTrue_thenTwoObjectsAreEqualAndHaveSameHashCodeIfAllFieldsIncludingParentsFieldsAreSame() {
+        Manager manager = new Manager("Opto", 444, "Nimi", 15, 22);
+        Manager managerTwo = new Manager("Opto", 444, "Nimi", 15, 22);
+        Manager managerThree = new Manager("Opto", 444, "Nimi", 15, 23);
+
+        assertEquals(manager, managerTwo);
+        assertNotEquals(managerTwo, managerThree);
+
+    }
+
+    @Test
+    public void whenUsingEqualsAndHashCodeAndCallSuperIsFalse_thenTwoObjectsAreEqualAndHaveSameHashCodeEvenIfAllParentsFieldsAreNotSame() {
+        ManagerV2 manager = new ManagerV2("Opto", 444, "Nimi", 15, 22);
+        ManagerV2 managerTwo = new ManagerV2("Opto", 444, "Nimi", 15, 22);
+        ManagerV2 managerThree = new ManagerV2("Opto", 444, "Nimi", 14, 21);
+        assertEquals(manager, managerTwo);
+        assertEquals(managerTwo, managerThree);
+    }
+}