Using Lambda Expression to foreach a List object in Java

In this tutorial, I will show you all how using Lambda Expression to foreach a List object in Java.

OK, let’s get started!

Usually from Java 7 and earlier, whenever you want to print out elements in a List object, for example:

List<String> names = new ArrayList<>();
names.add("Khanh");
names.add("Tan");
names.add("Thanh");

List<String> names = new ArrayList<>();

names.add("Khanh");

names.add("Tan");

names.add("Thanh");

We usually code as follows:

for (int i = 0; i < names.size(); i++) {
    System.out.println(names.get(i));
}

for (int i = 0; i < names.size(); i++) {

System.out.println(names.get(i));

}

or:

for (String s : names) {
    System.out.println(s);
}

for (String s : names) {

System.out.println(s);

}

Since Java 8, we have several other ways to do this: using the forEach () method in the List object with the Lambda Expression, detail as below:

names.forEach(s -> System.out.println(s));

1	names.forEach(s -> System.out.println(s));

or with Method reference:

names.forEach(System.out::println);

1	names.forEach(System.out::println);

The argument of forEach () method in the List object is the Consumer, a Functional Interface.

Result:

Khanh
Tan
Thanh

Khanh

Tan

Thanh

Virtual thread in Java