import java.util.*;
class Person implements Comparable<Person>
{
private static int count = 0; // static (class) variables
protected String name; // instance variables
protected int age; // instance variables
public Person()
{
//System.out.println(“Person Constructor”); // this(“”, 0); error: call to this must be first statemenht in constructor
this(“”, 0);
}
public Person(String name, int age)
{
count++;
this.name = name;
this.age = age;
}
public Person(Person other)
{
this(other.name, other.age);
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
public int getAge()
{
return age;
}
public void setAge(int age)
{
this.age = age;
}
@Override
public boolean equals(Object other) // Object.equals overriding
{
if (other instanceof Person) {
Person that = (Person) other;
return that.canEqual(this) && this.getName().equals(that.getName()) && this.getAge() == that.getAge();
}
return false;
}
@Override
public int hashCode() {
return (41 * getName().hashCode() + getAge());
}
public boolean canEqual(Object other) {
return (other instanceof Person);
}
@Override
public String toString() // Object.toString() overriding
{
return “Person Name: ” + name + ” Age: ” + age;
}
public void print() // instance methods
{
System.out.println(“Person Name: ” + name + ” Age: ” + age);
}
public void set(String name, int age)
{
this.name = name;
this.age = age;
}
public void set(Person other)
{
this.name = other.name;
this.age = other.age;
}
public Person clone()
{
Person p = new Person(this.name, this.age);
return p;
}
public static void printCount() // static (class) methods
{
System.out.println(“Person Count: ” + count);
}
public static int getCount() { return count; } // static (class) methods
public static void setCount(int value) { count = value; } // static (class) methods
public int compareTo(Person other)
{
String thisName = this.getName().toUpperCase();
String otherName = ((Person)other).getName().toUpperCase();
//ascending order
return thisName.compareTo(otherName);
//descending order
//return otherName.compareTo(thisName);
}
public static Comparator<Person> AgeComparator
= new Comparator<Person>() {
public int compare(Person p1, Person p2) {
int age1 = p1.getAge();
int age2 = p2.getAge();
//ascending order
return age1 – age2;
//descending order
//return age2 – age1;
}
};
}
///////////////////////////////////////////////////////////////////////////////////////
class Student extends Person
{
private static int count = 0; // static (class) variables
protected int id;
public Student()
{
id = 5208;
}
public Student(String name, int age, int id)
{
super(name, age);
this.id = id;
count++;
}
public int getID()
{
return id;
}
public void setID(int id)
{
this.id = id;
}
@Override
public boolean equals(Object other) // Object.equals overriding
{
if (other instanceof Student) {
Student that = (Student) other;
return that.canEqual(this) && this.getName().equals(that.getName()) && this.getAge() == that.getAge() && this.getID() == that.getID();
}
return false;
}
@Override
public int hashCode() {
return (41 * super.hashCode() + getID());
}
public boolean canEqual(Object other) {
return (other instanceof Student);
}
@Override
public String toString() // Object.toString() overriding
{
return “Student Name: ” + name + ” Age: ” + age + ” ID: ” + id;
}
public void superPrint()
{
super.print();
}
public void print() // Person class print() method overriding
{
System.out.println(“Student Name: ” + name + ” Age: ” + age + ” ID: ” + id);
}
public void set(String name, int age, int id)
{
super.set(name, age);
this.id = id;
}
public void set(String name, int age)
{
super.set(name, age);
}
public void set(Student other)
{
this.set(other.name, other.age, other.id);
}
public void set(Person other)
{
if (other instanceof Person)
super.set(other);
else
this.set((Student)other);
}
public Student clone()
{
Student s = new Student(this.name, this.age, this.id);
return s;
}
public static void printCount() // static (class) methods
{
System.out.println(“Student Count: ” + count);
}
public static int getCount() { return count; } // static (class) methods
public static void setCount(int value) { count = value; } // static (class) methods
public int compareTo(Student other)
{
String thisName = this.getName().toUpperCase();
String otherName = ((Student)other).getName().toUpperCase();
//ascending order
return thisName.compareTo(otherName);
//descending order
//return otherName.compareTo(thisName);
}
public static Comparator<Student> AgeComparator
= new Comparator<Student>() {
public int compare(Student p1, Student p2) {
int age1 = p1.getAge();
int age2 = p2.getAge();
//ascending order
return age1 – age2;
//descending order
//return age2 – age1;
}
};
public static Comparator<Student> IDComparator
= new Comparator<Student>() {
public int compare(Student p1, Student p2) {
int id1 = p1.getID();
int id2 = p2.getID();
//ascending order
return id1 – id2;
//descending order
//return id2 – id1;
}
};
}
class PersonStudentTest
{
public static void main(String[] args)
{
///////////////////////////////////////////////////////////////////////
Person jason1 = new Person(“Jason”, 10);
Person jason2 = new Person(“Jason”, 10);
Person jason3 = jason1;
Person jason4 = new Person(“Jason”, 20);
if (jason1 == jason2)
System.out.println(“jason1 == jason2”);
else
System.out.println(“jason1 != jason2”); //동일한 reference를 가리키지 않으므로 jason1 != jason2
if (jason1 == jason3)
System.out.println(“jason1 == jason3”); // 동일한 reference이므로 jason1 == jason3
else
System.out.println(“jason1 != jason3”);
if (jason1.equals(jason4))
System.out.println(“jason1 == jason4”);
else
System.out.println(“jason1 != jason4”); //동일한 reference를 가리키지 않으므로 jason1 != jason4
if (jason1.equals(jason2))
System.out.println(“jason1 equals to jason2”); // 내용이 같으므로 jason1 equals to jason2
else
System.out.println(“jason1 is not equal to jason2”);
if (jason1.equals(jason3))
System.out.println(“jason1 equals to jason3”); // 내용이 같으므로 jason1 equals to jason3
else
System.out.println(“jason1 is not equal to jason3”);
if (jason1.equals(jason4))
System.out.println(“jason1 equals jason4”);
else
System.out.println(“jason1 is not equal to jason4”); // 내용이 다르므로 jason1 is not equal to jason4
///////////////////////////////////////////////////////////////////////
Student john1 = new Student(“John”, 10, 100);
Student john2 = new Student(“John”, 10, 100);
Student john3 = john1;
Student john4 = new Student(“John”, 20, 100);
if (john1.equals(john2))
System.out.println(“john1 equals to john2”); // 내용이 같으므로 john1 equals to john2
else
System.out.println(“john1 is not equal to john2”);
if (john1.equals(john3))
System.out.println(“john1 equals to john3”); // 내용이 같으므로 jogn1 equals to john3
else
System.out.println(“john1 is not equal to john3”);
if (john1.equals(john4))
System.out.println(“john1 equals to john4”);
else
System.out.println(“john1 is not equal to john4”); // 내용이 다르므로 john1 is not equal to john4
Set<Student> sList5 = new HashSet<Student>();
sList5.add(john1);
sList5.add(john2);
sList5.add(john3);
sList5.add(john4);
sList5.forEach((s) -> System.out.println(s));
System.out.println(“sList5 contains john1 Student(\”John\”, 10, 100): ” + sList5.contains(john1));
System.out.println(“sList5 contains john2 Student(\”John\”, 10, 100): ” + sList5.contains(john2));
System.out.println(“sList5 contains john3 Student(\”John\”, 10, 100): ” + sList5.contains(john3));
System.out.println(“sList5 contains john4 Student(\”John\”, 20, 100):: ” + sList5.contains(john4));
System.out.println(“sList5 contains Student(\”John\”, 20, 100): ” + sList5.contains(new Student(“John”, 20, 100)));
System.out.println(“sList5 contains Student(\”John\”, 20, 200): ” + sList5.contains(new Student(“John”, 20, 200)));
Hashtable<Integer, Student> sList6 = new Hashtable<Integer, Student>();
sList6.put(1, john1);
sList6.put(2, john2);
sList6.put(3, john3);
sList6.put(4, john4);
sList6.forEach((i, s) -> System.out.println(s));
System.out.println(“sList5 contains john1 Student(\”John\”, 10, 100): ” + sList5.contains(john1));
System.out.println(“sList5 contains john2 Student(\”John\”, 10, 100): ” + sList5.contains(john2));
System.out.println(“sList5 contains john3 Student(\”John\”, 10, 100): ” + sList5.contains(john3));
System.out.println(“sList5 contains john4 Student(\”John\”, 20, 100):: ” + sList5.contains(john4));
System.out.println(“sList5 contains Student(\”John\”, 20, 100): ” + sList5.contains(new Student(“John”, 20, 100)));
System.out.println(“sList5 contains Student(\”John\”, 20, 200): ” + sList5.contains(new Student(“John”, 20, 200)));
}
}
