What is the Java operator called and what does it do

Question

I have been working with Java a couple of years  but up until recently I haven t run across this construct   int count   isHere   getHereCount index    getAwayCount index     This is probably a very simple question  but can someone explain it   How do I read it   I am pretty sure I know how it works    if isHere is true  getHereCount   is called   if isHere is false getAwayCount   is called    Correct   What is this construct called

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condition   truth   false    If the condition is true then evaluate the first expression  If the condition is false  evaluate the second expression   It is called the Conditional Operator and it is a type of Ternary Operation

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Actually it can take more than 3 arguments  For instance if we want to check wether a number is positive  negative or zero we can do this   String m  num  gt  0    is a POSITIVE NUMBER    num  lt  0   is a NEGATIVE NUMBER     IT s ZERO      which is better than using if  else if  else

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Not exactly correct  to be precise    if isHere is true  the result of getHereCount   is returned otheriwse the result of getAwayCount   is returned   That  returned  is very important  It means the methods must return a value and that value must be assigned somewhere   Also  it s not exactly syntactically equivalent to the if-else version  For example   String str1 str2 str3 str4  boolean check        return str1    check   str2   str3    str4    If coded with if-else will always result in more bytecode

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Correct  It s called the ternary operator  Some also call it the conditional operator

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Its Ternary Operator      The ternary operator is an operator that takes three arguments  The first  argument is a comparison argument  the second is the result upon a true  comparison  and the third is the result upon a false comparison

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This construct is called Ternary Operator in Computer Science and Programing techniques  And Wikipedia suggest the following explanation   In computer science  a ternary operator  sometimes incorrectly called a tertiary operator  is an operator that takes three arguments  The arguments and result can be of different types  Many programming languages that use C-like syntax feature a ternary operator       which defines a conditional expression   Not only in Java  this syntax is available within PHP  Objective-C too  In the following link it gives the following explanation  which is quiet good to understand it   A ternary operator is some operation operating on 3 inputs  It s a shortcut for an if-else statement  and is also known as a conditional operator  In Perl PHP it works as  boolean condition   true value   false value In C C   it works as  logical expression   action for true   action for false  This might be readable for some logical conditions which are not too complex otherwise it is better to use If-Else block with intended combination of conditional logic  We can simplify the If-Else blocks with this Ternary operator for one code statement line For Example  if   car isStarted            car goForward      else        car startTheEngine       Might be equal to the following    car isStarted       car goForward     car startTheEngine     So if we refer to your statement  int count   isHere   getHereCount index    getAwayCount index    It is actually the 100  equivalent of the following If-Else block  int count  if  isHere        count   getHereCount index     else       count   getAwayCount index      That s it   Hope this was helpful to somebody  Cheers

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Conditional expressions are in a completely different style  with no explicit if in the statement    The syntax is  boolean-expression   expression1   expression2    The result of this conditional expression is   expression1 if boolean-expression is true    otherwise the result is expression2    Suppose you want to assign the larger number of variable num1 and num2 to max  You can simply write a statement using the conditional expression  max    num1   num2    num1   num2   Note  The symbols   and   appear together in a conditional expression  They form a conditional operator and also called a ternary operator because it uses three operands  It is the only ternary operator in Java   cited from  Intro to Java Programming 10th edition by Y  Daniel Liang page 126 - 127

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According to the Sun Java Specification  it s called the Conditional Operator  See section 15 25  You re right as to what it does   The conditional operator     uses the boolean value of one expression to decide which of two other expressions should be evaluated   The conditional operator is syntactically right-associative  it groups right-to-left   so that a b c d e f g means the same as a b  c d  e f g     ConditionalExpression          ConditionalOrExpression         ConditionalOrExpression   Expression   ConditionalExpression   The conditional operator has three operand expressions    appears between the first and second expressions  and   appears between the second and third expressions   The first expression must be of type boolean or Boolean  or a compile-time error occurs

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Ternary  conditional  tomato  tomatoh   What it s really valuable for is variable initialization   If  like me  you re fond of initializing variables where they are defined  the conditional ternary operator  for it is both  permits you to do that in cases where there is conditionality about its value   Particularly notable in final fields  but useful elsewhere  too   e g    public class Foo       final double    value       public Foo boolean positive  double value            this value   positive   value   -value            Without that operator - by whatever name - you would have to make the field non-final or write a function simply to initialize it  Actually  that s not right - it can still be initialized using if else  at least in Java   But I find this cleaner

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Yes  it is a shorthand form of int count  if  isHere      count   getHereCount index   else     count   getAwayCount index    It s called the conditional operator  Many people  erroneously  call it the ternary operator  because it s the only ternary  three-argument  operator in Java  C  C    and probably many other languages  But theoretically there could be another ternary operator  whereas there can only be one conditional operator  The official name is given in the Java Language Specification     15 25 Conditional Operator     The conditional operator     uses the boolean value of one expression to decide which of two other expressions should be evaluated   Note that both branches must lead to methods with return values   It is a compile-time error for either the second or the third operand expression to be an invocation of a void method  In fact  by the grammar of expression statements    14 8   it is not permitted for a conditional expression to appear in any context where an invocation of a void method could appear   So  if doSomething   and doSomethingElse   are void methods  you cannot compress this  if  someBool      doSomething    else     doSomethingElse     into this  someBool   doSomething     doSomethingElse     Simple words  booleanCondition   executeThisPartIfBooleanConditionIsTrue   executeThisPartIfBooleanConditionIsFalse

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I happen to really like this operator  but the reader should be taken into consideration   You always have to balance code compactness with the time spent reading it  and in that it has some pretty severe flaws   First of all  there is the Original Asker s case   He just spent an hour posting about it and reading the responses   How longer would it have taken the author to write every    as an if then throughout the course of his entire life   Not an hour to be sure   Secondly  in C-like languages  you get in the habit of simply knowing that conditionals are the first thing in the line   I noticed this when I was using Ruby and came across lines like   callMethodWhatever Long   Expression   with   syntax  if conditional   If I was a long time Ruby user I probably wouldn t have had a problem with this line  but coming from C  when you see  callMethodWhatever  as the first thing in the line  you expect it to be executed   The    is less cryptic  but still unusual enough as to throw a reader off   The advantage  however  is a really cool feeling in your tummy when you can write a 3-line if statement in the space of 1 of the lines   Can t deny that     But honestly  not necessarily more readable by 90  of the people out there simply because of its  rarity    When it is truly an assignment based on a Boolean and values I don t have a problem with it  but it can easily be abused

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You might be interested in a proposal for some new operators that are similar to the conditional operator  The null-safe operators will enable code like this   String s   mayBeNull  toString       null     It would be especially convenient where auto-unboxing takes place   Integer ival            may be null int i   ival    -1      no NPE from unboxing   It has been selected for further consideration under JDK 7 s  Project Coin

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Others have answered this to reasonable extent  but often with the name  ternary operator    Being the pedant that I am  I d like to make it clear that the name of the operator is the conditional operator or  conditional operator      It s a ternary operator  in that it has three operands  and it happens to be the only ternary operator in Java at the moment   However  the spec is pretty clear that its name is the conditional  operator or  conditional operator     to be absolutely unambiguous  I think it s clearer to call it by that name  as it indicates the behaviour of the operator to some extent  evaluating a condition  rather than just how many operands it has

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int count   isHere   getHereCount index    getAwayCount index     means    if  isHere        count   getHereCount index     else       count   getAwayCount index

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Yes  you are correct      is typically called the  ternary conditional operator   often referred to as simply  ternary operator    It is a shorthand version of the standard if else conditional   Ternary Conditional Operator

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It s the conditional operator  and it s more than just a concise way of writing if statements    Since it is an expression that returns a value it can be used as part of other expressions

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