Basics and arrays Operators:  Arithmetic: +, -, *, /, %  Relational:, >=, ==, !=  Logical: &&, ||, ! Primitive data types Byte(8), short(16), int(32), long(64), float(32), double(64), boolean Numeric type conversion  float f = (float)10;  int I = (int)f;

Control structure Selection if( condition ) { statements; } else { statements; } Switch( integer) { Case 1: statements; Case 2: statements; … Default:.. } Repetition while( condition) { … } do { …. }while(condition); for ( x = 0; x < 10; x++) { statements; }

String type: String String is a predefined class in the Java library It is not primitive data type It is known as a reference type Declare a string  String message = “welcome!”; Concatenate strings  String s = “Chapter”+2;  message +=“ and Java is fun”; System.out.println(“i+j is” +(i+j)); // i=1, j = 2

Getting input from input Dialogs String input = JOptionPane.showInputDialog(null, “Enter an input”, “Input Dialog memo”, JOptionPane.QUESTION_MESSAGE); JOptionPane.showMessageDialog(null, input, “Example”, JOptionPane.INFORMATION_MESSAGE); Converting string to numbers  int val = Integer.parseInt(input);  double d = Double.parseDouble(input);

Methods Creating a method: modifier returntype methodname(list of parameters) { } public static int max( int int1, int int2) { if( int1 > int2) return int1; else retun int2; } primitive data are passed by value ( No Pointer!)

Calling a method int larger = max(3,4); System.out.println(max(3,4)); Static method can be called directly, it doesn’t need a class object to call it In the same class, it can be called by the method name In other class definition, it can be called by ClassName.max(3,4);

The Math class public static double sin(double x) public static double cos( double x) public static double exp( double a) public static double log( double a) public static double pow( double a, double b) public static double sqrt( double a) Min, max, abs and random methods

The random methed Math.random() generate a random double number 0<= Math.random <1.0 Generate random number between 0 and 9 int I = (int)(Math.random()*10); Generate number between 50 and 99 Int I = 50 + (int)(Math.random()*50); In genral, generate any random number between a and a+b, excluding a+b a + Math.random()*b

Generate random characters Every character has a unique Unicode between 0 and FFFF in hexadecimal (65535) in decimal Generate random integer between 0 – (int) (Math.random()*( ) Generate random lower case letter Unicode for a (int) ‘a’ Unicode for z is (int) ‘z’ Random letter between a-z (char) (‘a’ + Math.random()*(‘z’ =‘a’ +1))

Guess a number Write a program that generate a random number between Ask user to guess it, Print message that state either the number user guess is higher, lower Repeat until user enter the correct nmber.