foreach

问题 This question already has an answer here : Java8 Effectively Final compile time error on non final variable (1 answer) Closed 3 years ago . I am trying to return a boolean for the result. public boolean status(List<String> myArray) { boolean statusOk = false; myArray.stream().forEach(item -> { helpFunction(item).map ( x -> { statusOk = x.status(); // x.status() returns a boolean if (x.status()) { return true; } return false; }); }); } It's complaining variable used in lambda expression should

问题 Is that really true that i can use $_ as a dummy variable in foreach loop if there is no need for $value in foreach($array as $key => $value) ? I could not find any useful information that proves this except PHP syntax formatting. There's a special case for foreach loops when the value is not used inside the loop. In this case the dummy variable $_ (underscore) is used: foreach ($GLOBALS['TCA'] as $table => $_) { // Do something with $table } This is done for performance reasons, as it is

问题 Is that really true that i can use $_ as a dummy variable in foreach loop if there is no need for $value in foreach($array as $key => $value) ? I could not find any useful information that proves this except PHP syntax formatting. There's a special case for foreach loops when the value is not used inside the loop. In this case the dummy variable $_ (underscore) is used: foreach ($GLOBALS['TCA'] as $table => $_) { // Do something with $table } This is done for performance reasons, as it is

问题 Is that really true that i can use $_ as a dummy variable in foreach loop if there is no need for $value in foreach($array as $key => $value) ? I could not find any useful information that proves this except PHP syntax formatting. There's a special case for foreach loops when the value is not used inside the loop. In this case the dummy variable $_ (underscore) is used: foreach ($GLOBALS['TCA'] as $table => $_) { // Do something with $table } This is done for performance reasons, as it is

问题 Is that really true that i can use $_ as a dummy variable in foreach loop if there is no need for $value in foreach($array as $key => $value) ? I could not find any useful information that proves this except PHP syntax formatting. There's a special case for foreach loops when the value is not used inside the loop. In this case the dummy variable $_ (underscore) is used: foreach ($GLOBALS['TCA'] as $table => $_) { // Do something with $table } This is done for performance reasons, as it is

问题 In Java I have the following code List<Integer> myList = new ArrayList<>(); for (int i=0;i<9;i++) { myList.add(i); } Integer sum = 0; myList.forEach(i -> { sum = sum + i; // does not compile, sum needs to be final or effectively final }); for(int i : myList) { sum = sum + i; //runs without problems } My question is, why is it exactly that I cannot change the value of sum from within the lambda? It does the exact same thing as the for loop down below, or am I wrong? Interesting is also the

问题 In Java I have the following code List<Integer> myList = new ArrayList<>(); for (int i=0;i<9;i++) { myList.add(i); } Integer sum = 0; myList.forEach(i -> { sum = sum + i; // does not compile, sum needs to be final or effectively final }); for(int i : myList) { sum = sum + i; //runs without problems } My question is, why is it exactly that I cannot change the value of sum from within the lambda? It does the exact same thing as the for loop down below, or am I wrong? Interesting is also the

问题 In Java I have the following code List<Integer> myList = new ArrayList<>(); for (int i=0;i<9;i++) { myList.add(i); } Integer sum = 0; myList.forEach(i -> { sum = sum + i; // does not compile, sum needs to be final or effectively final }); for(int i : myList) { sum = sum + i; //runs without problems } My question is, why is it exactly that I cannot change the value of sum from within the lambda? It does the exact same thing as the for loop down below, or am I wrong? Interesting is also the

问题 I have an array of object some with same month name but different values based on day. How do we group array object based on same property value for example: [ { month: 'Jan', value: 3 }, { month: 'Jan', value: 3.5 }, { month: 'Feb', value: 2.1 }, { month: 'Mar', value: 6 }, { month: 'Apr', value: 4.3 }, { month: 'May', value: 5.5 }, { month: 'Jun', value: 7 }, { month: 'Jun', value: 9 }, { month: 'Jul', value: 7 }, { month: 'Jul', value: 9 }, { month: 'Jul', value: 7 }, { month: 'Aug', value

问题 I have an array of object some with same month name but different values based on day. How do we group array object based on same property value for example: [ { month: 'Jan', value: 3 }, { month: 'Jan', value: 3.5 }, { month: 'Feb', value: 2.1 }, { month: 'Mar', value: 6 }, { month: 'Apr', value: 4.3 }, { month: 'May', value: 5.5 }, { month: 'Jun', value: 7 }, { month: 'Jun', value: 9 }, { month: 'Jul', value: 7 }, { month: 'Jul', value: 9 }, { month: 'Jul', value: 7 }, { month: 'Aug', value