AP Computer Science A Unit 1 Primitive Types

University:
Amherst College
Course:
COSC 111 | Introduction to Computer Science I
Academic year:

2022
Views:

268

Pages:

3
Author:

Hallie Randolph

AP COMPUTER SCIENCE A Unit 1: Primitive Types Print statements and commenting: The System.out.print and System.out.println methods are used to send output for display on the screen. System.out.println moves cursor to new line after printing. Ex: System.out.println(“Hello”); System.out.print(“World”); Output: Hello World System.out.print does not move the cursor to a new line after printing. Ex: System.out.print(“Hello”); System.out.print(“World”); Output: Hello World To comment a single line use // Ex: //This is a return method To comment multiple lines use /* comment */ Ex: /* comments are ignored by computer */ Data Types: Type: Description: Examples: int integers 2, 5 , -3 double decimals 2.45 , 3.14, -8.1 boolean True or false True, false Operators: + addition - subtraction * multiplication / division % modulus Compound operators and increment and decrement: increment x++ x+=1 x= x + 1 decrement x-- x-=1 x= x - 1 Corresponding operator for arithmetic operators: Compound operator: Other way to write it: Example: += x= x + 4 x+=4 -= x= x - 4 x-=4 *= x= x * 4 x*=4 /= x= x / 4 x/=4 %= x= x % 4 x%=4 Casting: Values of a certain type can only be stored in a variable of that type. Casting is changing a bigger data type to a smaller data type. You must cast: double to integer if casting. Ex: double d = 5.25; int i = (int) d; To turn a decimal to int : Ex: int x = (int) 17.654 // Put the (data type) in front of the value to change it Example of mathematical operation: int x = 10; double y = 2 * x + 3; // y will store the value 23.0 Unit 2: Using Objects Objects: An object is created from a class by calling the class constructor along with the new keyword. The name of a constructor is the same as the name of the class it belongs to. If it is followed by a (possibly empty) list of values then those values are called parameters. The signature of a constructor consists of the name of the constructor along with the list of types of parameters that it expects. When calling the constructor, the parameter list provided must match the signature. Ex: The Rectangle class from the Java standard library contains, among others, the following two constructors: Rectangle(int width, int height) // first constructor and... Rectangle(int x, int y, int width, int height) // second constructor Valid constructor calls: new Rectangle(3, 6) // calls the first constructor new Rectangle(-1, 7, 3, 4) // calls the second constructor Not valid constructor calls: new Rectangle(7.45, 1) // invalid since the first parameter is double new Rectangle(1, 7, 3) // invalid since it has three parameters

AP Computer Science A Unit 1 Primitive Types

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