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Published byMatilda Cleopatra Wilkins Modified over 9 years ago
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Основы языка
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1.Переменные 2.Операторы 3.Примитивные типы 4.Массивы 5.Выражения 6.Блоки 7.Управление циклами
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Переменные Переменные объекта Переменные класса Локальные переменные Параметры Именование – $gear1, _gear, gear, gearRatio и NUM_GEARS – 1$gear, 1_gear, 1gear, int…
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Примитивные типы НазваниеМинимальное значениеМаксимальное значение byte-128127 short-32,76832,767 int-2,147,483,6482,147,483,647 long-9,223,372,036,854,775,8089,223,372,036,854,775,807 float32-bit double64-bit booleantrueFlase char\u0000 (0)\uffff (65,535 )
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Default Values Data TypeDefault Value (for fields) byte0 short0 int0 long0L float0.0f double0.0d char'\u0000' String (or any object) null booleanfalse
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Литералы boolean result = true; char capitalC = 'C'; byte b = 100; short s = 10000; int i = 100000; // The number 26, in decimal int decVal = 26; // The number 26, in hexadecimal int hexVal = 0x1a; // The number 26, in binary int binVal = 0b11010;
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double d1 = 123.4; // same value as d1, but in scientific //notation double d2 = 1.234e2; float f1 = 123.4f;
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Array // declares an array of integers int[] anArray; // allocates memory for 10 integers anArray = new int[10]; // initialize first element anArray[0] = 100; // initialize second element anArray[1] = 200;
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Операторы OperatorsPrecedence postfixexpr++ expr-- unary++expr --expr +expr -expr ~ ! multiplicative* / % additive+ - shift > >>> relational = instanceof equality== != bitwise AND& bitwise exclusive OR^ bitwise inclusive OR| logical AND&& logical OR|| ternary? : assignment= += -= *= /= %= &= ^= |= >= >>>=
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Выражения и блоки Выражение if (value1 == value2) System.out.println("value1 == value2"); Statements // assignment statement float aValue = 8933.234f; Блоки if (condition) { // begin block 1 int q = 0; System.out.println("Condition is true."); } // end block one
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Блоки if-then if (isMoving){ // the "then" clause: decrease // current speed currentSpeed--; } if-then-else if (isMoving) { currentSpeed--; } else { System.err.println("The bicycle has already stopped!"); } switch int month = 8; String monthString; switch (month) { case 1: monthString = "January"; break; case 2: monthString = "February"; break; default: monthString = "Invalid month"; break; } System.out.println(monthString);
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while and do-while while (expression) { statement(s) } do { statement(s) } while (expression); for for (initialization; termination; increment) { statement(s) } int[] numbers = {1,2,3,4,5,6,7,8,9,10}; for (int item : numbers) { System.out.println("Count is: " + item); }
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break for (i = 0; i < arrayOfInts.length; i++) { if (arrayOfInts[i] == searchfor) { foundIt = true; break; } Continue for (int i = 0; i < max; i++) { // interested only in p's if (searchMe.charAt(i) != 'p') continue; // process p's numPs++; } return
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