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Today’s topic: Arithmetic expressions
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Arithmetic expressions
binary (two arguments) arithmetic operators +, -, *, /, % (mod or modulus) unary (one arg) operators -, + Order of operations just like you’d expect: Please Excuse My Dear Aunt Sadie. Can user () to override.
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Arithmetic expressions
How would we code the following? Let n be 2 and k be 2n+1.
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Arithmetic expressions
How would we code the following? Let n be 2 and k be 2n+1. int n = 2; int k = 2*n+1; Or int n, k; n = 2; k = 2 * n + 1;
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Arithmetic expressions
How would we code the following? Let n be 2 and k be 2n+1. int n = 2; int k = 2*n+1; Note: The rhs of the equals is always evaluated first and is assigned to the lhs. Therefore, you cannot say: int 2 = n; Or 2*n+1 = k;
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Arithmetic expressions
Example from physics: F = M A (force = mass x acceleration). How would we code this in Java?
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Arithmetic expressions
Example from physics: F = M A (force = mass x acceleration). How would we code this in Java? double mass = 12.0; double acc = 13.9; double force = mass * acceleration; System.out.println( “force = “ + force );
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Differences between int and double
int (integer) and double (real numbers) are different. int is a subset of double but ints are much faster to calculate than doubles So use ints whenever you can but be aware of the following: int n = 5/2; int k = 9/10;
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Differences between int and double
5 is an int. 5.1 is a double. 5.0 is a double. 5.7f is a float Range of values: int -2 billion to +2 billion double 4.9x to 1.8x10308 float 1.4x10-45 to 3.4x1038
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Converting doubles to ints
When we convert, we will typically lose something. Consider converting 12.9 to an int. There is no int 12.9. So the compiler will issue a message. To inform the compiler that we really wish to do this, we can use a cast. int i; double d = 12.9; i = (int) d; //What do you think is in i now?
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Converting doubles to ints
int i; double d = 12.9; i = (int) d; //What do you think is in i now? //how can we round instead?
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ints and mod (%) What is the result of the following: int k = 5 / 2;
What is the remainder? % is used to calculate the remainder. int remainder = 5 % 2;
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Float vs. double Recall range of values:
double 4.9x to 1.8x10308 float 1.4x10-45 to 3.4x1038 Recall that we used a cast to convert a double to an int: double d = 12.9; int i = (int) d; This is because a double won’t fit into an int. Will a double fit into a float?
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Increment and decrement operators (++ and --)
What does the following do: int i = 12; i = i + 2;
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Increment and decrement operators (++ and --)
We often see code like the following: int value = 12; … value = value + 1;
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Increment and decrement operators (++ and --)
We often see code like the following: int value = 12; … value = value + 1; int value = 12; … value++; //post increment ++value; //pre increment value++;
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Increment and decrement operators (++ and --)
We often see code like the following: int value = 12; … value = value - 1; int value = 12; … value--; //post decrement --value; //pre decrement value--;
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Increment and decrement operators (++ and --)
We can use these operators in expressions as well (but don’t get carried away): int where = 92; int k = 7; where = k++; int j = --where;
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Convert the following to Java expressions:
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Write a program that . . . class MyProgramTemplate { public static void main ( String param[] ) { System.out.println( "hi there" ); } //end main } //end class
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Write a program that . . . Declares a variable for the radius of a circle with a value of 12.7. Calculates the circumference. Calculates the area. Prints out the radius, circumference, and area. class MyProgramTemplate { public static void main ( String param[] ) { System.out.println( "hi there" ); } //end main } //end class
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Write a program that . . . Declares a variable for the radius of a circle with a value of 12.7. Calculates the circumference. Calculates the area. Prints out the radius, circumference, and area. class MyProgramTemplate { public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of 12.7. //Calculate the circumference. //Calculate the area. //Print out the radius, circumference, and area. } //end main } //end class
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Write a program that . . . class MyProgramTemplate { public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of //Calculate the circumference. //Calculate the area. //Print out the radius, circumference, and area. } //end main } //end class What types of things are radius, circumference, and area?
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Write a program that . . . public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. //Calculate the area. //Print out the radius, circumference, and area. } //end main
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Write a program that . . . public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = ?; //Calculate the area. //Print out the radius, circumference, and area. } //end main
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Write a program that . . . public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * 3.14 * radius; //Calculate the area. //Print out the radius, circumference, and area. } //end main
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Write a program that . . . public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. //Print out the radius, circumference, and area. } //end main
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Write a program that . . . public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. double area = Math.PI * radius * radius; //Print out the radius, circumference, and area. } //end main
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Write a program that . . . public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. double area = Math.PI * radius * radius; //Print out the radius, circumference, and area. System.out.println( " radius = " + radius ); ? } //end main
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Write a program that . . . public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. double area = Math.PI * radius * radius; //Print out the radius, circumference, and area. System.out.println( " radius = " + radius ); System.out.println( " circumference = " + circ ); System.out.println( " area = " + area ); System.out.println( " Bye."); } //end main
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Write a program that . . . public static void main ( String param[] ) { System.out.println( "hi there" ); //Declare a variable for the radius of a circle with a value of double radius = 12.7; //Calculate the circumference. double circ = 2 * Math.PI * radius; //Calculate the area. double area = Math.PI * radius * radius; //Print out the radius, circumference, and area. System.out.print( " radius = " + radius + ", " ); System.out.print( " circumference = " + circ + ", " ); System.out.println( " area = " + area + "." ); System.out.println( " Bye."); } //end main
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