2.8 Wrapper Classes - Integer & Double | CSAwesome APCSA Java

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The Integer class and Double class are wrapper classes that create objects from primitive types.

The following Integer methods and constructors, including what they do and when they are used, are part of the Java Quick Reference.

Integer(value): Constructs a new Integer object that represents the specified int value.

Integer.MIN_VALUE : The minimum value represented by an int or Integer.

Integer.MAX_VALUE : The maximum value represented by an int or Integer.

int intValue() : Returns the value of this Integer as an int.

The following Double methods and constructors, including what they do and when they are used, are part of the Java Quick Reference Guide given during the exam:

Double(double value) : Constructs a new Double object that represents the specified double value.

double doubleValue() : Returns the value of this Double as a double.

Autoboxing is the automatic conversion that the Java compiler makes between primitive types and their corresponding object wrapper classes. This includes converting an int to an Integer and a double to a Double.

The Java compiler applies autoboxing when a primitive value is:

Passed as a parameter to a method that expects an object of the corresponding wrapper class.

Assigned to a variable of the corresponding wrapper class.

Unboxing is the automatic conversion that the Java compiler makes from the wrapper class to the primitive type. This includes converting an Integer to an int and a Double to a double.

The Java compiler applies unboxing when a wrapper class object is:

Passed as a parameter to a method that expects a value of the corresponding primitive type.

Assigned to a variable of the corresponding primitive type.