[9-1] equals () 오버라이딩

class Exercise9_1 {
public static void main (String[] args) {
SutdaCard c1 = new SutdaCard (3, true);
SutdaCard c2 = new SutdaCard (3, true);

System.out.println("c1="+c1);
System.out.println("c2="+c2);
System.out.println("c1.equals (c2) : "+c1.equals (c2) );
}
}

class SutdaCard {
int num;
boolean isKwang;

SutdaCard () {
this (1, true);
}

SutdaCard (int num, boolean isKwang) {
this.num = num;
this.isKwang = isKwang;
}

public boolean equals (Object obj) {
if (obj instanceof SutdaCard) {
SutdaCard s = (SutdaCard)obj;
return num == s.num && isKwang == s.isKwang;
}
return false;
}

public String toString () {
return num + (isKwang ? "K":" ");
}
}