Examples of converting Java 7 code to Java 8 code

Converting a for loop to a stream

In Java 7, you would use a for loop to iterate over a collection of elements. In Java 8, you can use a stream to do the same thing. Here is an example:

// Java 7
for (String element : collection) {
  // do something with element
}

// Java 8
collection.stream().forEach(element -> {
  // do something with element
});

Converting an if statement to a filter

In Java 7, you would use an if statement to filter a collection of elements. In Java 8, you can use a filter to do the same thing. Here is an example:

// Java 7
List<String> filteredList = new ArrayList<>();
for (String element : collection) {
  if (element.length() > 5) {
    filteredList.add(element);
 }
}

// Java 8  
List<String> filteredList = collection.stream().filter(element ->
  element.length() > 5).collect(Collectors.toList());

Converting a map to a reduce

In Java 7, you would use a map to create a new collection of elements. In Java 8, you can use a reduce to do the same thing. Here is an example:

// Java 7
Map<String, Integer> map = new HashMap<>();
for (String element : collection) {
  map.put(element, 1);
}

// Java 8 
Map<String, Integer> map =
  collection.stream().collect(Collectors.toMap(element -> element, element -> 1));

I hope this helps!

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