Move to next item using Java 8 foreach loop in stream

Question

I have a problem with the stream of Java 8 foreach attempting to move on next item in loop  I cannot set the command like continue   only return  works but you will exit from the loop in this case  I need to move on next item in loop  How can I do that   Example not working    try Stream lt String gt  lines   Files lines path  StandardCharsets ISO 8859 1                filteredLines   lines filter      foreach line - gt                              if                    continue     this command doesn t working here             Example working    try Stream lt String gt  lines   Files lines path  StandardCharsets ISO 8859 1        filteredLines   lines filter      collect Collectors toList        for String filteredLine   filteredLines             if            continue     it s working

User · Answer

The lambda you are passing to forEach   is evaluated for each element received from the stream   The iteration itself is not visible from within the scope of the lambda  so you cannot continue it as if forEach   were a C preprocessor macro   Instead  you can conditionally skip the rest of the statements in it

User · Answer

Using return  will work just fine   It will not prevent the full loop from completing   It will only stop executing the current iteration of the forEach loop   Try the following little program   public static void main String   args        ArrayList lt String gt  stringList   new ArrayList lt  gt         stringList add  a        stringList add  b        stringList add  c         stringList stream   forEach str - gt            if  str equals  b    return     only skips this iteration           System out println str               Output      a   c   Notice how the return  is executed for the b iteration  but c prints on the following iteration just fine   Why does this work   The reason the behavior seems unintuitive at first is because we are used to the return statement interrupting the execution of the whole method   So in this case  we expect the main method execution as a whole to be halted   However  what needs to be understood is that a lambda expression  such as   str - gt        if  str equals  b    return       System out println str           really needs to be considered as its own distinct  method   completely separate from the main method  despite it being conveniently located within it  So really  the return statement only halts the execution of the lambda expression   The second thing that needs to be understood is that   stringList stream   forEach         is really just a normal loop under the covers that executes the lambda expression for every iteration   With these 2 points in mind  the above code can be rewritten in the following equivalent way  for educational purposes only    public static void main String   args        ArrayList lt String gt  stringList   new ArrayList lt  gt         stringList add  a        stringList add  b        stringList add  c         for String s   stringList            lambdaExpressionEquivalent s            private static void lambdaExpressionEquivalent String str        if  str equals  b              return             System out println str       With this  less magic  code equivalent  the scope of the return statement becomes more apparent

User · Answer

Another solution  go through a filter with your inverted conditions   Example    if subscribtion isOnce    amp  amp  subscribtion isCalled                     continue      can be replaced with   filter s - gt    s isOnce    amp  amp  s isCalled       The most straightforward approach seem to be using  return   though

User · Answer

You can use a simple if statement instead of continue  So instead of the way you have your code  you can try   try Stream lt String gt  lines   Files lines path  StandardCharsets ISO 8859 1                filteredLines   lines filter      foreach line - gt                              if                          Code you want to run                            Once the code runs  it will continue anyway             The predicate in the if statement will just be the opposite of the predicate in your if pred  continue  statement  so just use    logical not

[java] Move to next item using Java 8 foreach loop in stream

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