CPSC 233 Tutorial Xin Jan 24, 2011

Assignment 1 Due on Jan 28 at 4:00 PM Part I  Assignment Box on 2 nd floor Part II  Submitted electronically on UNIX Submit submit -c -a eg. submit -c 233 -a 3 README.txt List submitted files showstuff -c -a eg. showstuff -c 233 -a 3 Submit early and update

Keyboard Input Again Scanner.nextLine() will pick up any leftovers If Scanner.nextInt() was called previously, nextLine() usually pickup a carriage-return (CR) use an extra nextLine() to get rid of the CR Experiments with MyInput.java Input 20 and see the results Input 20 abc and see the results

Pick up chars String str = in.nextLine(); char c = str.charAt(0); What other methods String has? Search in Google with class String java API using documents provided by oracle.com

Switch statement char x = ‘a’; int val; switch (x) { case ‘a’: val = 0; // fall through case ‘b’: val = 1; break; case ‘c’: // fall through case ‘C’: // do the same for ‘c’ and ‘C’ val = 3; break; default: val = 4; } Fall through: Without an explicit break statement, the execution continues on the next case!!! This can be used to do the same thing for a few values.

Operator precedence An example int v = 92 int x = 100 | 25 & 36 << & 55 * ++ v; = 100 | ((25 & (36 << (2 + 12))) & (55 * (++ v))) Extremely confusing Sometimes results are dependent on the specific complier (for c/c++) Avoid by all means Clarify with parentheses until it is easy to understand by common humans

Common Java Operators / Operator Precedence Precedence level OperatorDescriptionAssociativity 1expression++ expression-- Post-increment Post-decrement Right to left 2++expression --expression + - ! ~ (type) Pre-increment Pre-decrement Unary plus Unary minus Logical negation Bitwise complement Cast Right to left

Common Java Operators / Operator Precedence Precedence level OperatorDescriptionAssociativity 3*/%*/% Multiplication Division Remainder/modulus Left to right Addition or String concatenation Subtraction Left to right 5<< >> Left bitwise shift Right bitwise shift Left to right

Common Java Operators / Operator Precedence Precedence level OperatorDescriptionAssociativity 6< <= > >= Less than Less than, equal to Greater than Greater than, equal to Left to right 7= != Equal to Not equal to Left to right 8&Bitwise ANDLeft to right 9^Bitwise exclusive ORLeft to right

Common Java Operators / Operator Precedence Precedence level OperatorDescriptionAssociativity 10|Bitwise ORLeft to right 11&&Logical ANDLeft to right 12||Logical ORLeft to right

Common Java Operators / Operator Precedence Precedence level OperatorDescriptionAssociativity 13= += -= *= /= %= &= ^= |= <<= >>= Assignment Add, assignment Subtract, assignment Multiply, assignment Division, assignment Remainder, assignment Bitwise AND, assignment Bitwise XOR, assignment Bitwise OR, assignment Left shift, assignment Right shift, assignment Right to left

x ++ vs. ++x public class IncOperators { public static void main (String [] args) { int x = 8; System.out.println("x = " + x); int returnedValue = ++ x; System.out.println("the returned value is: " + returnedValue); System.out.println("x after the operation is: " + x); }

x ++ vs. ++x public class Order2 { public static void main (String [] args) { int num1; int num2; num1 = 5; num2 = ++num1 * num1++; System.out.println("num1=" + num1); System.out.println("num2=" + num2); }

type cast Double  int float x = 5; // OK float x = 5.0;// Illegal float x = 5.f; // OK int x = 5.0; // Illegal int x = (int) 5.f; // OK double x = 5 / 2; // x = 2 double x = 5 / (double)2; // x = 2.5 char  int char c = 97; // OK int x = ‘a’; // OK char c = ‘a’ + 1; // OK

bitwise operations ~ & | ^ > ~ = & = | = ^ = << = >> = >> = 0010

Showing integers in binary public class ShowBinary { public static void main (String [] args) { showInt(3); } public static void showInt(int x) { for (int i = 0; i < 32; i ++) { if ((x & 0x ) == 0) System.out.print("0"); else System.out.print("1"); x = x << 1; }

Experiments with the program public static void main (String [] args) { int x = 3; System.out.println("x = " + x + " in binary: "); showInt(x); System.out.println(); int y = -2011; System.out.println("y = " + y + " in binary: "); showInt(y); System.out.println(); System.out.println("x AND y in binary: "); showInt(x & y); System.out.println(); }