Differences in boolean operators vs and vs

Question

I know the rules for  amp  amp  and    but what are  amp  and    Please explain these to me with an example

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While the basic difference is that  amp  is used for bitwise operations mostly on long  int or byte where it can be used for kind of a mask  the results can differ even if you use it instead of logical  amp  amp    The difference is more noticeable in some scenarios    Evaluating some of the expressions is time consuming Evaluating one of the expression can be done only if the previous one was true The expressions have some side-effect  intended or not    First point is quite straightforward  it causes no bugs  but it takes more time  If you have several different checks in one conditional statements  put those that are either cheaper or more likely to fail to the left   For second point  see this example   if   a    null   amp   a isEmpty       This fails for null  as evaluating the second expression produces a NullPointerException  Logical operator  amp  amp  is lazy  if left operand is false  the result is false no matter what right operand is   Example for the third point -- let s say we have an app that uses DB without any triggers or cascades  Before we remove a Building object  we must change a Department object s building to another one  Let s also say the operation status is returned as a boolean  true   success   Then   if  departmentDao update department  newBuilding   amp  buildingDao remove building     This evaluates both expressions and thus performs building removal even if the department update failed for some reason  With  amp  amp   it works as intended and it stops after first failure   As for a    b  it is equivalent of    a  amp  amp   b   it stops if a is true  no more explanation needed

User · Answer

amp  and   are bitwise operators on integral types  e g  int   http   download oracle com javase tutorial java nutsandbolts op3 html   amp  amp  and    operate on booleans only  and short-circuit  as other answers have already said

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Those are the bitwise AND and bitwise OR operators  int a   6     110 int b   4     100     Bitwise AND      int c   a  amp  b       110     amp  100    -----      100     Bitwise OR  int d   a   b       110      100    -----      110  System out println c      4 System out println d      6  Thanks to Carlos for pointing out the appropriate section in the Java Language Spec  15 22 1  15 22 2  regarding the different behaviors of the operator based on its inputs  Indeed when both inputs are boolean  the operators are considered the Boolean Logical Operators and behave similar to the Conditional-And   amp  amp   and Conditional-Or      operators except for the fact that they don t short-circuit so while the following is safe  if  a    null   amp  amp   a something    3       This is not  if  a    null   amp   a something    3        quot Short-circuiting quot  means the operator does not necessarily examine all conditions  In the above examples   amp  amp  will examine the second condition only when a is not null  otherwise the whole statement will return false  and it would be moot to examine following conditions anyway   so the statement of a something will not raise an exception  or is considered  quot safe  quot  The  amp  operator always examines every condition in the clause  so in the examples above  a something may be evaluated when a is in fact a null value  raising an exception

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If an expression involving the Boolean  amp  operator is evaluated  both operands are evaluated  Then the  amp  operator is applied to the operand    When an expression involving the  amp  amp  operator is evaluated  the first operand is evaluated   If the first operand evaluates to false  the evaluation of the second operand is skipped   If the first operand returns a value of true then the second operand is evaluated  If the second operand returns a value of true then  amp  amp  operator is then applied to the first and second operands   Similar for   and

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Maybe it can be useful to know that the bitwise AND and bitwise OR operators are always evaluated before conditional AND and conditional OR used in the same expression   if    1 gt 2   amp  amp   2 gt 1    true     false

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I think you re talking about the logical meaning of both operators  here you have a table-resume   boolean a  b   Operation     Meaning                       Note ---------     -------                       ----    a  amp  amp  b     logical AND                    short-circuiting    a    b     logical OR                     short-circuiting    a  amp   b     boolean logical AND            not short-circuiting    a    b     boolean logical OR             not short-circuiting    a    b     boolean logical exclusive OR    a          logical NOT  short-circuiting         x    0   amp  amp   1 x  gt  1    SAFE not short-circuiting     x    0   amp    1 x  gt  1    NOT SAFE   Short-circuit evaluation  minimal evaluation  or McCarthy evaluation  after John McCarthy  is the semantics of some Boolean operators in some programming languages in which the second argument is executed or evaluated only if the first argument does not suffice to determine the value of the expression  when the first argument of the AND function evaluates to false  the overall value must be false  and when the first argument of the OR function evaluates to true  the overall value must be true   Not Safe means the operator always examines every condition in the clause  so in the examples above  1 x may be evaluated when the x is  in fact  a 0 value  raising an exception

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amp  amp       are logical operators     short circuit   amp      are boolean logical operators      Non-short circuit  Moving to differences in execution on expressions  Bitwise operators evaluate both sides irrespective of the result of left hand side  But in the case of evaluating expressions with logical operators  the evaluation of the right hand expression is dependent on the left hand condition   For Example   int i   25  int j   25  if i    lt  0  amp  amp  j    gt  0      System out println  OK    System out printf  i    d   j    d  i j     This will print i 26   j 25   As the first condition is false the right hand condition is bypassed as the result is false anyways irrespective of the right hand side condition  short circuit   int i   25  int j   25  if i    lt  0  amp  j    gt  0      System out println  OK    System out printf  i    d   j    d  i j     But  this will print i 26  j 26

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amp  and   provide the same outcome as the  amp  amp  and    operators  The difference is that they always evaluate both sides of the expression where as  amp  amp  and    stop evaluating if the first condition is enough to determine the outcome

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In Java  the single operators  amp           depend on the operands  If both operands are ints  then a bitwise operation is performed  If both are booleans  a  logical  operation is performed   If both operands mismatch  a compile time error is thrown   The double operators  amp  amp      behave similarly to their single counterparts  but both operands must be conditional expressions  for example   if    a  lt  0    amp  amp    b  lt  0            or similarly  if    a  lt  0        b  lt  0             source  java programming lang 4th ed

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The operators  amp  amp  and    are short-circuiting  meaning they will not evaluate their right-hand expression if the value of the left-hand expression is enough to determine the result

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I know there s a lot of answers here  but they all seem a bit confusing  So after doing some research from the Java oracle study guide  I ve come up with three different scenarios of when to use  amp  amp  or  amp   The three scenarios are logical AND  bitwise AND  and boolean AND   Logical AND  Logical AND  aka Conditional AND  uses the  amp  amp  operator  It s short-circuited meaning  if the left operand is false  then the right operand will not be evaluated  Example   int x   0  if  false  amp  amp   1      x        System out println  Inside of if      System out println x       0    In the above example the value printed to the console of x will be 0  because the first operand in the if statement is false  hence java has no need to compute  1      x  therefore x will not be computed   Bitwise AND  Bitwise AND uses the  amp  operator  It s used to preform a bitwise operation on the value  It s much easier to see what s going on by looking at operation on binary numbers ex   int a   5                            5 in binary is 0101 int b   12                          12 in binary is 1100 int c   a  amp  b     bitwise  amp  preformed on a and b is 0100 which is 4   As you can see in the example  when the binary representations of the numbers 5 and 12 are lined up  then a bitwise AND preformed will only produce a binary number where the same digit in both numbers have a 1  Hence 0101  amp  1100    0100  Which in decimal is 5  amp  12    4   Boolean AND  Now the boolean AND operator behaves similarly and differently to both the bitwise AND and logical AND  I like to think of it as preforming a bitwise AND between two boolean values  or bits   therefore it uses  amp  operator  The boolean values can be the result of a logical expression too    It returns either a true or false value  much like the logical AND  but unlike the logical AND it is not short-circuited  The reason being  is that for it to preform that bitwise AND  it must know the value of both left and right operands  Here s an ex   int x   0  if  false  amp   1      x        System out println  Inside of if      System out println x      1    Now when that if statement is ran  the expression  1      x  will be executed  even though the left operand is false  Hence the value printed out for x will be 1 because it got incremented   This also applies to Logical OR       bitwise OR      and boolean OR      Hope this clears up some confusion

[java] Differences in boolean operators: & vs && and | vs ||

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