What is the difference between and in Java

Question

I always thought that  amp  amp  operator in Java is used for verifying whether both its boolean operands are true  and the  amp  operator is used to do Bit-wise operations on two integer types   Recently I came to know that  amp  operator can also be used verify whether both its boolean operands are true  the only difference being that it checks the RHS operand even if the LHS operand is false   Is the  amp  operator in Java internally overloaded  Or is there some other concept behind this

User · Answer

It depends on the type of the arguments     For integer arguments  the single ampersand    amp   is the  bit-wise AND  operator  The double ampersand    amp  amp    is not defined for anything but two boolean arguments   For boolean arguments  the single ampersand constitutes the  unconditional   logical AND  operator while the double ampersand    amp  amp    is the  conditional logical AND  operator  That is to say that the single ampersand always evaluates both arguments whereas the double ampersand will only evaluate the second argument if the first argument is true   For all other argument types and combinations  a compile-time error should occur

User · Answer

Besides  amp  amp  and    being short circuiting  also consider operator precedence when mixing the two forms  I think it will not be immediately apparent to everybody that result1 and result2 contain different values   boolean a   true  boolean b   false  boolean c   false   boolean result1   a    b  amp  amp  c    is true   evaluated as a     b  amp  amp  c  boolean result2   a    b  amp  amp  c    is false  evaluated as  a   b   amp  amp  c

User · Answer

Besides not being a lazy evaluator by evaluating both operands  I think the main characteristics of bitwise operators compare each bytes of operands like in the following example   int a   4  int b   7  System out println a  amp  b      prints 4   meaning in an 32 bit system    00000000 00000000 00000000 00000100    00000000 00000000 00000000 00000111                                           00000000 00000000 00000000 00000100

User · Answer

With booleans  there is no output difference between the two  You can swap  amp  amp  and  amp  or    and   and it will never change the result of your expression   The difference lies behind the scene where the information is being processed  When you right an expression   a    0   amp    b    0    for a  0 and b   1  The following happens   left side  a    0 -- gt  false right side  b 1  0 -- gt  true left side and right side are both true  -- gt  false expression returns false   When you write an expression  a    0   amp  amp    b    0  when a  0 and b   1  the following happens   a    0 -- gt false expression returns false   Less steps  less processing  better coding  especially when doing many boolean expression or complicated arguments

User · Answer

amp  amp  and    are called short circuit operators  When they are used  for    - if the first operand evaluates to true  then the rest of the operands are not evaluated  For  amp  amp  - if the first operand evaluates to false  the rest of them don t get evaluated at all   so if  a       x  gt  0   in this example the variable x won t get incremented if a was true

User · Answer

amp  is a bitwise operator plus used for checking both conditions because sometimes we need to evaluate both condition  But  amp  amp  logical operator go to 2nd condition when first condition give true

User · Answer

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

User · Answer

it s as specified in the JLS  15 22 2    When both operands of a  amp      or   operator are of type boolean or Boolean  then the type of the bitwise operator expression is boolean  In all cases  the operands are subject to unboxing conversion    5 1 8  as necessary  For  amp   the result value is true if both operand values are true  otherwise  the result is false  For    the result value is true if the operand values are different  otherwise  the result is false  For    the result value is false if both operand values are false  otherwise  the result is true   The  quot trick quot  is that  amp  is an Integer Bitwise Operator as well as an Boolean Logical Operator  So why not  seeing this as an example for operator overloading is reasonable

User · Answer

amp   lt -- verifies both operands  amp  amp   lt -- stops evaluating if the first operand evaluates to false since the result will be false   x    0   amp   1 x  gt  1   lt -- this means evaluate  x    0  then evaluate  1 x  gt  1  then do the  amp   the problem is that for x 0 this will throw an exception    x    0   amp  amp   1 x  gt  1   lt -- this means evaluate  x    0  and only if this is true then evaluate  1 x  gt  1  so if you have x 0 then this is perfectly safe and won t throw any exception if  x    0  evaluates to false the whole thing directly evaluates to false without evaluating the  1 x  gt  1    EDIT   exprA   exprB  lt -- this means evaluate exprA then evaluate exprB then do the     exprA    exprB  lt -- this means evaluate exprA and only if this is false then evaluate exprB and do the

User · Answer

all answers are great  and it seems that no more answer is needed but I just wonted to point out something about  amp  amp  operator called dependent condition  In expressions using operator  amp  amp   a condition   we   ll call this the dependent condition   may require another condition to be true for the evaluation of the dependent condition to be meaningful    In this case  the dependent condition should be placed after the  amp  amp  operator to prevent errors   Consider the expression  i    0   amp  amp   10   i    2   The dependent condition  10   i    2  must appear after the  amp  amp  operator to prevent the possibility of division by zero   another example   myObject    null   amp  amp   myObject getValue      somevaluse    and another thing   amp  amp  and    are called short-circuit evaluation because the second argument is executed or evaluated only if the first argument does not suffice to determine the value of the expression  References  Java    How To Program  Early Objects   Tenth Edition

User · Answer

I think my answer can be more understandable   There are two differences between   amp  and  amp  amp    If they use as logical AND   amp  and  amp  amp  can be logical AND  when the  amp  or  amp  amp  left and right expression result all is true  the whole operation result can be true   when  amp  and  amp  amp  as logical AND  there is a difference   when use  amp  amp  as logical AND  if the left expression result is false  the right expression will not execute   Take the example    String str   null   if str  null  amp  amp   str equals           the right expression will not execute      If using  amp    String str   null   if str  null  amp   str equals           the right expression will execute  and throw the NullPointerException       An other more example   int x   0  int y   2  if x  0  amp    y gt 2       System out print    y     y       print is  y 3       int x   0  int y   2  if x  0  amp  amp    y gt 2       System out print    y     y       print is  y 2      amp  can be used as bit operator   amp  can be used as Bitwise AND operator    amp  amp  can not      The bitwise AND    amp   operator produces 1 if and only if both of the bits in    its operands are 1  However  if both of the bits are 0 or both of the bits are different then this operator produces 0  To be more precise bitwise AND    amp   operator  returns 1 if any of the two bits is 1 and it returns 0 if any of the bits is 0      From the wiki page   http   www roseindia net java master-java java-bitwise-and shtml

User · Answer

amp  amp       - is a Logical AND operator produce a boolean value of true or false based on the logical relationship of its arguments   For example  - Condition1  amp  amp  Condition2  If Condition1 is false  then  Condition1  amp  amp  Condition2  will always be false  that is the reason why this logical operator is also known as Short Circuit Operator because it does not evaluate another condition  If Condition1 is false   then there is no need to evaluate Condtiton2   If Condition1 is true  then Condition2 is evaluated  if it is true then overall result will be true else it will be false       amp       - is a Bitwise AND Operator  It produces a one  1  in the output if both the input bits are one  Otherwise it produces zero  0    For example -  int a 12     binary representation of 12 is 1100  int b 6     binary representation of 6 is 0110  int c  a  amp  b      binary representation of  12  amp  6  is 0100  The value of c is 4   for reference   refer this http   techno-terminal blogspot in 2015 11 difference-between-operator-and-operator html

User · Answer

amp  amp  is a short circuit operator whereas  amp  is a AND operator   Try this       String s   null      boolean b   false  amp  s isEmpty       NullPointerException     boolean sb   false  amp  amp  s isEmpty       sb is false

[java] What is the difference between & and && in Java?

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