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Java Forum / First Aid / December 2005If statement - whats going on here?
Hiya ok peeps, we all know how normal if statements work, but how does this work? What should be expected from the outcome? boolean brandNew = false if (brandNew) //condition 1 else { //condition 2 } >ok peeps, we all know how normal if statements work, but how does this >work? What should be expected from the outcome? [quoted text clipped - 6 lines] > //condition 2 > } 1. you left off your semicolon after false 2. your conditions are empty 3. but other than that, if brandNew is true, you execute condition 1 else condition 2. The {} are mandatory if your condition has more than one statement  SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > Hiya > [quoted text clipped - 8 lines] > //condition 2 > } It will execute the 'else' statement. > Hiya > [quoted text clipped - 8 lines] > //condition 2 > } You need a statement where the comment "//condition 1" appears. At the very least, you'd have to put the empty statement, like so: if (brandNew) ; //condition 1 else { //condition 2 } In the revised example, what will happen is that since brandNew is false, the else branch gets taken. - Oliver > Hiya > [quoted text clipped - 8 lines] > //condition 2 > } Maybe I'm dense, but what part of this are you considering "not normal"? I could take this a few different ways. If I'm supposed to take this as pseudo-code and pretend there are statements where the comments currently reside, then .... if '//condition 1' is a single statement, it executes normally. if '//condition 1' is empty or has multiple lines, you will get a compiler complaint that there's an else with no if attached. I typed all that without actually trying to compile the code. Afterwards, I thought I'd check myself. Here is the code, which you could *easily* have written and played with yourself, rather than asking the group. I was right about the results, fwiw. public class IfTest { public static void main (String [] args) { boolean brandNew = false; if (brandNew) brandNew = true; //condition 1 else { //condition 2 } } } Signaturemonique Ask smart questions, get good answers: http://www.catb.org/~esr/faqs/smart-questions.html > Hiya > [quoted text clipped - 8 lines] > //condition 2 > } "What should be expected from the outcome?" A compilation error. > Hiya > [quoted text clipped - 8 lines] > //condition 2 > } The same way. if (brandNew) is the same as saying if (brandNew == true) It's just a shorthand way of doing it. That's just something you have to get used to. I never think of it, so I use the "== true" one, usually. SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. > > Hiya > > [quoted text clipped - 17 lines] > It's just a shorthand way of doing it. That's just something you have to > get used to. I never think of it, so I use the "== true" one, usually. <SCCCE> public class BooleanTest { private boolean someWord = true; private String testFailed = "testFailed"; public static void main(String[] args) { BooleanTest bt = new BooleanTest(); bt.doTheTest(); System.exit(0); } public void doTheTest() { if (someWord) { System.out.print(someWord); } else { System.out.print(testFailed); } } } </SCCCE> SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. On Mon, 5 Dec 2005 23:30:49 -0600, Noodles Jefferson <silverbells@tacoshells.com> wrote, quoted or indirectly quoted someone who said : >The same way. > [quoted text clipped - 3 lines] > >It's just a shorthand way of doing it It is not shorthand. IF wants a boolean expression. brandNew is already a boolean expression. Adding a string of == true is just stuttering. When do you stop? if ( brandnew == true == true == true == true ) What you are advocating is as goofy as suggesting that i = j; should be replaced by i = j+0; because you don't understand that j is a int expression already. This is one of my pet peeves. See http://mindprod.com/jgloss/boolean.html and http://mindprod.com/jgloss/newbie.html SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > On Mon, 5 Dec 2005 23:30:49 -0600, Noodles Jefferson > <silverbells@tacoshells.com> wrote, quoted or indirectly quoted [quoted text clipped - 10 lines] > It is not shorthand. IF wants a boolean expression. brandNew is > already a boolean expression. Okay. Fair enough. > Adding a string of == true is just stuttering. When do you stop? > > if ( brandnew == true == true == true == true ) Well, now you're just being a c**k. That will throw a compiler error because you're not testing 4 expressions and you don't need to test it 4 times to determine if it's true or false. So you can't do it anyway. > What you are advocating is as goofy as suggesting that > i = j; > should be replaced by > i = j+0; First, I'm not advocating it, she(?) asked how it works. People telling OP that it'll throw an error are either wrong or lying to him. > because you don't understand that j is a int expression already. Secondly, when you adding nothing to something, you get the the same number so why would you do that anyway? > This is one of my pet peeves. I'm sorry if your pets are peeved. > See > http://mindprod.com/jgloss/boolean.html > and > http://mindprod.com/jgloss/newbie.html SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. Noodles Jefferson wrote On 12/06/05 17:06,: >>On Mon, 5 Dec 2005 23:30:49 -0600, Noodles Jefferson >><silverbells@tacoshells.com> wrote, quoted or indirectly quoted [quoted text clipped - 20 lines] > because you're not testing 4 expressions and you don't need to test it 4 > times to determine if it's true or false. So you can't do it anyway. Of the three assertions in this paragraph, two are easily disproved by experiment. But if you're Really Sure -- well, would you like to place a small wager? As to the first assertion, Usenet is not a good medium for assessing someone's skills in food preparation. SignatureEric.Sosman@sun.com > Noodles Jefferson wrote On 12/06/05 17:06,: > > [quoted text clipped - 26 lines] > easily disproved by experiment. But if you're Really > Sure -- well, would you like to place a small wager? Nah. People that want to put money think they're gonna keep it. I'm not so sure. In blackjack terms, I'll stand at 16. > As to the first assertion, Usenet is not a good > medium for assessing someone's skills in food preparation. I make the best french toast in the universe. Tell no one. SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. >> if ( brandnew == true == true == true == true ) > > Well, now you're just being a c**k. That will throw a compiler error > because you're not testing 4 expressions and you don't need to test it 4 > times to determine if it's true or false. So you can't do it anyway. I'm relatively sure that you CAN do this, and that it WON'T throw a compiler error (assuming that after the if statement, there is a statement). In other words, yes the above will not compile, but it's not because of the fact that there are "4 expressions" in a row. >> What you are advocating is as goofy as suggesting that >> i = j; [quoted text clipped - 3 lines] > First, I'm not advocating it, she(?) asked how it works. People telling > OP that it'll throw an error are either wrong or lying to him. I'm one of the people who told the OP that the code (s)he posted will not compile. The reason it won't compile is that if-statements have to contain a statement. So the following: <code> if (someCondition) else statementB; </code> won't compile, but this: <code> if (someCondition) statementA; else statementB; </code> will compile (assuming some suitable replacement for "statementA" and "statementB"). The actual code that the OP posted was: <code> if (brandNew) //condition 1 else { //condition 2 } </code> And here, the else branch does contain a statement ("{}" is a legal statement in Java), but the if branch did not contain a statement, which is why I said it would not compile. - Oliver > will compile (assuming some suitable replacement for "statementA" and > "statementB"). [quoted text clipped - 12 lines] > statement in Java), but the if branch did not contain a statement, which is > why I said it would not compile. Which is exactly why I expressed reservations when posting *my* response. It all hinges on whether '//condition 1' is really code, and if so, how many lines of code that block might be. Signaturemonique Ask smart questions, get good answers: http://www.catb.org/~esr/faqs/smart-questions.html > >> if ( brandnew == true == true == true == true ) > > [quoted text clipped - 6 lines] > In other words, yes the above will not compile, but it's not because of the > fact that there are "4 expressions" in a row. Ok, what about something like this if (someBoolean == true == false == true == false) How does something like that work out then? > >> What you are advocating is as goofy as suggesting that > >> i = j; [quoted text clipped - 39 lines] > statement in Java), but the if branch did not contain a statement, which is > why I said it would not compile. I have nothing to add to this. I don't know why I'm telling you that I'm not adding anything here. SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. > Ok, what about something like this > > if (someBoolean == true == false == true == false) > > How does something like that work out then? Not sure. Why don't you try it and see? What happens is well defined in the language spec (google for "Java Language Specification"), in the sense that the order of evaluation is left to right, and so on, but I'm too lazy to try it myself, and I don't want to risk giving an incorrect prediction here. - Oliver > > Ok, what about something like this > > [quoted text clipped - 9 lines] > > - Oliver deesBoolean tested using == true == false == true deesBoolean started true - tested false datBoolean tested using == true == false == true datBoolean started false - tested true. Ooookay. Well, that was pretty worthless. Lost was a rerun anyway so whatever. SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. > deesBoolean tested using == true == false == true > deesBoolean started true - tested false Yep, you had (parens added for clarity): ((((deesBoolean) == true) == false) == true) You said deesBoolean was true, so it goes like this. Turn off any proportional fonts. The underlines above each line show what section will be simplified in the next line. ___________ ((((deesBoolean) == true) == false) == true) _____________ ((((true ) == true) == false) == true) ____________________ ((( true == true) == false) == true) _______________________ ((( true ) == false) == true) _______________________ (( true == false) == true) __________________________________ (( false ) == true) ____________________________ ( false == true) ____________________________________________ ( false ) _____ false > datBoolean tested using == true == false == true > datBoolean started false - tested true. You can work this one out for practice. Signaturewww.designacourse.com The Easiest Way To Train Anyone... Anywhere. Chris Smith - Lead Software Developer/Technical Trainer MindIQ Corporation > > deesBoolean tested using == true == false == true > > deesBoolean started true - tested false [quoted text clipped - 25 lines] > _____ > false Sweet explanation. Thanks. > > datBoolean tested using == true == false == true > > datBoolean started false - tested true. > > You can work this one out for practice. SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM NP: "The Road to Chicago" -- Thomas Newman (Road to Perdition Soundtrack) "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. > Well, now you're just being a c**k. That will throw a compiler error > because you're not testing 4 expressions and you don't need to test it 4 > times to determine if it's true or false. So you can't do it anyway. What compiler are you using? Its valid java, and in fact I don't know how a compiler would even detect that its nonsense code. marks:~ mehaase$ cat Test.java class Test { public static void main(String args[]) { boolean b = false; if (b == true == true == true) System.out.println("FOO"); else System.out.println("BAR"); } } marks:~ mehaase$ javac Test.java marks:~ mehaase$ java Test BAR See? Works fine here |\/| /| |2 |< mehaase(at)gmail(dot)com In article <mehaase-286CCB.02142407122005@news1.east.earthlink.net>, Mark Haase took the hamburger, threw it on the grill, and I said "Oh wow"... > > Well, now you're just being a c**k. That will throw a compiler error > > because you're not testing 4 expressions and you don't need to test it 4 [quoted text clipped - 19 lines] > > See? Works fine here New to me. Why in the hell would someone do something like that? SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. On Wed, 7 Dec 2005 16:14:16 -0600, Noodles Jefferson <silverbells@tacoshells.com> wrote, quoted or indirectly quoted someone who said : >Why in the hell would someone do something like that? you were the one defending it, adding == true on the end of a perfectly valid boolean expression. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > On Wed, 7 Dec 2005 16:14:16 -0600, Noodles Jefferson > <silverbells@tacoshells.com> wrote, quoted or indirectly quoted [quoted text clipped - 4 lines] > you were the one defending it, adding == true on the end of a > perfectly valid boolean expression. Not 4 of them. 1, I can see. Not 4. SignatureNoodles Jefferson mhm31x9 Smeeter#29 WSD#30 sTaRShInE_mOOnBeAm aT HoTmAil dOt CoM "Our earth is degenerate in these latter days, bribery and corruption are common, children no longer obey their parents and the end of the world is evidently approaching." --Assyrian clay tablet 2800 B.C. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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