How to implement hashCode(), equal() and compare()

Index

Related

TLDR

---

class Recepi {
	String name;
	int difficulty ;
	String[] ingredients;
}

HashCode

@Override
public int hashCode() {
	int result = 17
	result *= 31 * name.hashCode();
	result *= 31 * difficulty.hashCode();
	result *= 31 * ingredients.hashCode();
	return result
}
 

---

Equals

@Overrride
public boolean equals(Object o) {
	if (this == 0) return true;
	if (o == null) return false;
	if (this.getClass() != o.getClass()) return false;
 
	Ricetta that = (Ricetta) o;
	return Object.equals(name, that.name) &&
		   Object.equals(difficulty, that.difficulty) &&
		   Object.equals(ingredients, that.ingredients);
}

• Per confrontare tipi primitivi si usa: ==
• Per confrontare degli array si usa: ?
• Per confrontare enum si usa: ?
• per confrontare oggetti si usa: equals()

Compare

in questo confronterò la difficoltà

@Override
public int compareTo(Recepi o) {
	if (this.difficulty > o.difficulty)
		return 1
	
	if (this.difficulty < o.difficulty)
		return -1
	
	else return 0
}