powerpoint presentation · data conversion: • narrowing or widening • assignment • promotion...
TRANSCRIPT
ECE 122
Course Website: http://www.ecs.umass.edu/ece/ece122/
Piazza: https://piazza.com/umass/spring2017/ece122
TA Office Hours
Wed 4:30PM - 6:00PM
Thu 4:30PM - 6:00PM
Fri 3:00PM - 6:00PM
Location: Marston 34
ECE 122- LAB
Outline:
Compile-time vs Run-time error
Data conversion
Operator precedence
Scanner classes
Classes and Objects
Compile-time error
• Syntax errors
• Mismatch in datatypes
See example CompileError1.java & CompileError2.java
Run-time error
• Exceptions
See example RunError.java & InputOutput.java
Data Conversion:
• Narrowing or Widening• Assignment
• Promotion
• Casting
See example Dataconv.java & Temperature.java
Ref: MargretPosch, Java Basics - Promotion and Casting, https://www.youtube.com/watch?v=FNPEKwQUJwU
Ref: MargretPosch, Java Basics - Promotion and Casting, https://www.youtube.com/watch?v=FNPEKwQUJwU
Ref: MargretPosch, Java Basics - Promotion and Casting, https://www.youtube.com/watch?v=FNPEKwQUJwU
Data Conversion:
far = 40.0
celsius0 = 5 / 9 * (far - 32);
= 5/9 * (40.0 – 32)
= 5/9 * 8.0
= 0 * 8.0 = 0.0 * 8.0 = 0.0
celsius1 = (double) 5 / 9 * (far - 32);
= (double) 5/9 * (40.0 – 32)
= (double) 5/9 * 8.0
= 5.0 / 9 * 8.0
= 0.555 * 8.0 = 4.444
Operator precedence See example Arithmetic.java
Scanner classes:
int nextInt() Returns the next token as an int.
long nextLong() Returns the next token as a long
float nextFloat() Returns the next token as a float
double nextDouble() Returns the next token as a double
String nextLine() Returns the rest of the current line, excluding any line separator at the end.
Classes and Objects
• Creating objectsSee example BankAccount.java
• ReferencesSee example BankAccountref.java
Customer1
Customer2
1111
1050.75
Customer1
Customer2
2222
2020.29
Before
After
Practice
• Write a program that accepts 3 numbers (1 integer, 1 float,1 double ) through standard input and print the average of numbers.
• Create a Person class with class variables Date ,month, year
Create two objects pA,pB of Person class.
Assign values to these class variables and print the date of birth of 2 persons in mm/dd/yy format.