如何使用Stream Java 8将列表中的元素转换为字符串

Question

I have only one element in List<String> and I want to convert that to a String using Stream in Java 8

I tried this

public static void main(String[] args) {
    List<String> lineList = Arrays.asList("This is a test line");
    String lineString;
    lineString = lineList.stream().map(element -> lineString);
}

Answer 1

This does what you've asked, in an unsafe way mind you, and also you should pay heed to the comments you've received.

public static void main(String[] args) {
    List<String> lineList = Arrays.asList("This is a test line");
    String lineString;
    lineString = lineList.stream().findFirst().get();
}

Answer 2

You can use reduce to get one transformed element from a list like this for example :

List<String> lineList = Arrays.asList("This is a test line");
String lineString = lineList.stream().reduce("", (res, s) -> res + s);

It will work if you have 1 or many elements in lineList array and you can set the transformation in the lambda expression.

Answer 3

Try this :
public class Test {

        public static void main(String[] args) {
            List<String> lineList = Arrays.asList("This is a test line");
            String lineString;
            lineString = lineList.stream().map(Object::toString)
                    .collect(Collectors.joining(", "));
            System.out.println(lineString);
    }

}