Java : Consumer with Examples
Consumer (Java SE 19 & JDK 19) API Examples.
You will find code examples on most Consumer methods.
Summary
final var stream = Stream.of("a", "b", "c");
final var action = new Consumer<String>() {
@Override
public void accept(String s) {
System.out.println(s.toUpperCase().repeat(3));
}
};
// AAA
// BBB
// CCC
stream.forEach(action);
// An example with a lambda expression.
final var stream = Stream.of("a", "b", "c");
// AAA
// BBB
// CCC
stream.forEach(s -> System.out.println(s.toUpperCase().repeat(3)));
Methods
void accept (T t)
final var consumer = new Consumer<String>() {
@Override
public void accept(String s) {
System.out.println(s.toUpperCase());
}
};
consumer.accept("abcd"); // ABCD
final var consumer = new Consumer<LocalDate>() {
@Override
public void accept(LocalDate date) {
System.out.println(date);
}
};
consumer.accept(LocalDate.of(1999, 1, 1)); // 1999-01-01
// An example with a lambda expression.
final var list = List.of("AAA", "BBB", "CCC");
System.out.println(list); // [AAA, BBB, CCC]
// aaa
// bbb
// ccc
list.forEach(s -> System.out.println(s.toLowerCase()));
default Consumer<T> andThen (Consumer<? super T> after)
final var consumer1 = new Consumer<String>() {
@Override
public void accept(String s) {
System.out.println(s);
}
};
final var after = new Consumer<String>() {
@Override
public void accept(String s) {
System.out.println(s.toUpperCase());
}
};
final var consumer2 = consumer1.andThen(after);
// abcd
// ABCD
consumer2.accept("abcd");
final var consumer1 = new Consumer<String>() {
@Override
public void accept(String s) {
if (s == null) {
throw new IllegalArgumentException("s is null");
}
System.out.println("accept : " + s);
}
};
final var after = new Consumer<String>() {
@Override
public void accept(String s) {
System.out.println("after : " + s);
}
};
final var consumer2 = consumer1.andThen(after);
consumer2.accept(null);
// Result
// ↓
// java.lang.IllegalArgumentException: s is null