Java 8 Default Methods - Default Method Examples

public interface Employee {

    String getName();

    String getDept();

    BigDecimal getSalary();

    default BigDecimal getBonus() {
        return getSalary().multiply(new BigDecimal(0.10)).
                setScale(2, BigDecimal.ROUND_HALF_UP);
    }

    default String getEmployeeInfo() {
        return "Name: " + getName() +
                ", Dept: " + getDept() +
                ", Salary " + getSalary() +
                ", Bonus " + getBonus();
    }

    static String getEmployeeInfo(List<Employee> employeeList) {
        String info = "";
        for (Employee employee : employeeList) {
            info += employee.getEmployeeInfo() + "\n";
        }
        return info;
    }
}

import java.math.BigDecimal;

public interface BonusCalculator {

    BigDecimal getSalary();

    BigDecimal getBonusPercent();

    default BigDecimal getBonus() {
        return getSalary().multiply(getBonusPercent())
                .divide(new BigDecimal(100));
    }
}

public interface IEnum<E extends Enum<E>> {

    int ordinal();

    default E next() {
        E[] ies = this.getAllValues();
        return this.ordinal() != ies.length - 1 ? ies[this.ordinal() + 1] : null;
    }

    default E previous() {
        return this.ordinal() != 0 ? this.getAllValues()[this.ordinal() - 1] : null;
    }

    @SuppressWarnings("unchecked")
    private E[] getAllValues() {//java 9 private methods in interface
        IEnum[] ies = this.getClass().getEnumConstants();
        return (E[]) ies;
    }
}