Difference between: variable = br.readLine()... vs br.readLine()...

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Podstawy Java, Poziom 5, Lekcja 12

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Hi, can anybody explain me what is the difference between these two constructions?

String s;
       while (!(s = reader.readLine()).equals("exit")) {
           try {
           if (s.contains(".")) {

String s;
      while (!(reader.readLine()).equals("exit")) {
          s = reader.readLine();
          try {
          if (s.contains(".")) {
              print(Double.parseDouble(s));

The first case works as expected (after entering "exit" the program stops working). The second one behaves in a different way (doesn't stop the program after entering "exit"). Why both of these constructions don't work at the same way? In both cases we check if a user input equals "exit". After that variable s is set to reader.readLine().

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Lisa L

Poziom 47 , Nuremberg, Germany

12 czerwca 2022, 08:48

The second reads two lines in each iteration. The first readLine call checks for the line to equal 'exit'. If yes, it breaks out of the loop. The read line gets thrown away. Then the second call to readLine saves the line in the variable s (a reference to that line to be precise). Then you do some calculation with it. If now the first line is 'some text' and the second line is the only occurrence of 'exit', then your loop will run forever.