Advanced Programming in Java

Advanced Programming in JavaSadegh AliakbarySharif University of TechnologyFall 2012AgendaReviewUser inputScannerStrong type checkingOther flow-control structuresswitchbreak & continueStringsArrays

Fall 2012Sharif University of Technology2ReviewVariablesPrimitive data typesOperatorsMethodsParameter passingCall by valueConditionsIf, else, else ifLoopswhiledo-whileforFall 2012Sharif University of Technology3User InputPrint on consoleSystem.out.printlnHow to read from console?ScannerExample:Scanner scanner = new Scanner(System.in);int n = scanner.nextInt();double d = scanner.nextDouble();

Fall 2012Sharif University of Technology4ExampleScanner scanner = new Scanner(System.in);int a = scanner.nextInt();int b = scanner.nextInt();long pow = power(a,b);System.out.println(pow);Fall 2012Sharif University of Technology5Type CheckingJava has a strong type-checking mechanismSome assignment is not permitted

int intVal = 2;long longVal =12;

intVal = longVal;Syntax ErrorlongVal = intVal;OKintVal = (int)longVal; OK (Type Casting)Fall 2012Sharif University of Technology6Direct Type ConversionThe arrows are transitiveAll other conversions need an explicit castboolean is not convertiblechar is a special typeFall 2012Sharif University of Technology7bytecharshortintlongfloatdoublebooleanType Conversion GridFall 2012Sharif University of Technology8

Reference: http://docstore.mik.ua/orelly/java-ent/jnut/ch02_04.htm#javanut3-ch-2-tab-4

8Type ConversionFall 2012Sharif University of Technology9N : the conversion cannot be performedY : the conversion is performed automatically and implicitly by JavaC : the conversion is a narrowing conversion and requires an explicit castY* : the conversion is an automatic widening conversion, but that some of the least significant digits of the value may be lost by the conversion

9Examplei = 123456789; //a big integerf = i; //f stores and approximation of iSystem.out.println(f);//output : 1.23456792E8i = (int) f;System.out.println(i); //output : 123456792

floating-point types are approximations of numbers They cannot always hold as many significant digits as the integer typesFall 2012Sharif University of Technology10Floating Point, Some NotesDouble.NaNdouble nan = 0.0/0.0;Infinitydouble inf = Double.MAX_VALUE*2;Negative infinitydouble inf = Double.MAX_VALUE*(-2);Double.NEGATIVE_INFINITYDouble.POSITIVE_INFINITYFormatting a doubleSystem.out.format("min double = %5.2f%n", ff);ComparisonCompare doublesUsing == with float or double is an anti-patternAn infinite loop:for (float f = 10f; f != 0; f -= 0.1) {System.out.println(f);}

Fall 2012Sharif University of Technology12Numeric AssignmentsNumeric SuffixDouble d = 123.54d;Float f = 123f;Long l = 123123 l; byte b = 127;//NothingAssignment OverflowLarge long to intLower bits are usedNo runtime errorLarge double to integerBrings a max intSwitch statementAn alternative to if-elseBetter structureBefore Java 1.7When the condition is a numeric or an ordinal variableWith Java 1.7Strings are also allowedFall 2012Sharif University of Technology14switch exampleswitch (i) {case 1:System.out.println("1");break;case 2:System.out.println("2");break;default:System.out.println("default");}

Fall 2012Sharif University of Technology15Scanner scanner = new Scanner(System.in);boolean again = true;while(again){System.out.println("1: Play");System.out.println("2: Setting:");System.out.println("3: Exit");System.out.print("Enter Your Choice:");int i = scanner.nextInt();switch (i) {case 1:play();break;case 2:setting();break;case 3:again = false;break;default:System.out.println("Enter a valid number");}}Fall 2012Sharif University of Technology16BreakBreaks the execution of a loop

while(true){int nextInt = scanner.nextInt();if(nextInt==0)break;...}Fall 2012Sharif University of Technology17ContinueStops the execution of the body of the loop and continues from the beginning of the loop

for(int i=0;i