import import import import in Java

Painting Code 3 of 9 in Java import import import import

static javalangSystemin; static javalangSystemout; javautilScanner; javautilRandom;

class DontTellThemTheyLost { public static void main(String args[]) { Scanner myScanner = new Scanner(in); outprint( Enter an int from 1 to 10: ); int inputNumber = myScannernextInt(); int randomNumber = new Random()nextInt(10) + 1; if (inputNumber == randomNumber) { outprintln( *You win* ); } outprintln( That was a very good guess :-) ); outprint( The random number was ); outprintln(randomNumber + ); outprintln( Thank you for playing ); } } The if statement in Listing 5-2 has no else part When inputNumber is the same as randomNumber, the computer prints You win When inputNumber is different from randomNumber, the computer doesn t print You win

Figure 5-3: Two runs of the game in Listing 5-2

Listing 5-2 illustrates another new idea With an import declaration for Systemin, I can reduce new Scanner(Systemin) to the shorter new Scanner(in) Adding this import declaration is hardly worth the effort In fact, I do more typing with the import declaration than without it Nevertheless, the code in Listing 5-2 demonstrates that it s possible to import Systemin

The Java programming language has plenty of little squiggles and doodads for your various condition-forming needs This section tells you all about them

Table 5-1

is equal to is not equal to is less than is greater than is less than or equal to is greater than or equal to

numberOfCows == 5 buttonClicked != panicButton numberOfCows < 5 myInitial > B numberOfCows <= 5 myInitial >= B

You can use all Java s comparison operators to compare numbers and characters When you compare numbers, things go pretty much the way you think they should go But when you compare characters, things are a little strange Comparing uppercase letters with one another is no problem Because the letter B comes alphabetically before H, the condition B < H is true Comparing lowercase letters with one another is also okay What s strange is that when you compare an uppercase letter with a lowercase letter, the uppercase letter is always smaller So, even though Z < A is false, Z < a is true Under the hood, the letters A through Z are stored with numeric codes 65 through 90 The letters a through z are stored with codes 97 through 122 That s why each uppercase letter is smaller than each lowercase letter Be careful when you compare two numbers for equality (with ==) or inequality (with !=) After doing some calculations and obtaining two double values or two float values, the values that you have are seldom dead-on equal to one another (The problem comes from those pesky digits beyond the decimal point) For instance, the Fahrenheit equivalent of 21 degrees Celsius is 698, and when you calculate 90 / 5 * 21 + 32 by hand, you get 698 But the condition 90 / 5 * 21 + 32 == 698 turns out to be false That s because, when the computer calculates 90 / 5 * 21 + 32, it gets 6980000000000001, not 698

When you start working with objects, you find that you can use == and != to compare objects with one another For instance, a button that you see on the computer screen is an object You can ask whether the thing that was just mouse-clicked is a particular button on your screen You do this with Java s equality operator if (egetSource() == bCopy) { clipboardsetText(whichgetText()); To find out more about responding to button clicks, read 16 on this book s CD-ROM The big gotcha with Java s comparison scheme comes when you compare two strings (For a word or two about Java s String type, see the section about reference types in 4) When you compare two strings with one another, you don t want to use the double equal sign Using the double equal sign would ask, Is this string stored in exactly the same place in memory as that other string That s usually not what you want to ask Instead, you usually want to ask, Does this string have the same characters in it as that other