Wrapper

👎🏻 Limit of Primitive type

• 1️⃣ primitive type is not an instance
• cannot use collection framework

• 2️⃣ cannot use null

• 👍🏻 Advantage of primitive type: faster than wrapper type

✅ Wrapper

• Reference type: use equals()
• immutable
• 값을 바꿀 때마다 새로운 인스턴스 생성

✅ Boxing, Unboxing

• Boxing: primitive type ➡️ wrapper type(reference)
• Unboxing: wrapper ➡️ primitive type

Integer wrapper = Integer.valueOf(10); //Integer 10
int primitive = newInteger.intValue(); //int 10

✅ AutoBoxing

• valueOf, intValue() 없이 그냥 primitive type ➡️ reference type으로 자동으로 바꿔준다

//auto-boxing
Integer wrapper = 10;

//auto-unboxing
int primitive = wrapper;

✅ Wrapper Methods

Integer i1 = Integer.valueOf("10"); //String -> Integer(wrapper)
int i2 = Integer.parseInt("10"); //String -> int(primitive)

i1.compareTo(20);
Integer.sum(10, 20); //30
Integer.min(10, 20); //10
Integer.max(10, 20); //20

✅

✅

✅

✅

✅