Java8: four functional interfaces (consumer, supplier, function, predict)

1、 Consumer interface ：Consumer

（1） Functional interface

@FunctionalInterface
public interface Consumer<T> {
/**
* Performs this operation on the given argument.
*
* @param t the input argument
*/
void accept(T t);

Test class

 public void happy(String string, Consumer<String> con) {
con.accept(string);
}
@Test
public void test1() {
happy("zhai", (m) -> System.out.println(" Hello " + m ));
}

 Hello zhai

Features of consumer interface ： There is input but no return value

 

2、 Supply type interface ：Supplier

（1） Functional interface

@FunctionalInterface
public interface Supplier<T> {
/**
* Gets a result.
*
* @return a result
*/
T get();
}

（2） test

 public List<Integer> getNumList(int num, Supplier<Integer> sup) {
List<Integer> list = new ArrayList<>();
for (int i = 0; i < num; i++) {
Integer n = sup.get();
list.add(n);
}
return list;
}
@Test
public void test2() {
List<Integer> numList = getNumList(10, () -> (int) (Math.random() * 100));
for (Integer num : numList) {
System.out.println(num);
}
}

75
1
61
85
97
25
94
41
24
90

No input parameters , Have output

 

3、 Functional interface ：Function

（1） Functional interface

@FunctionalInterface
public interface Function<T, R> {
/**
* Applies this function to the given argument.
*
* @param t the function argument
* @return the function result
*/
R apply(T t);

（2） test

@FunctionalInterface
public interface Function<T, R> {
/**
* Applies this function to the given argument.
*
* @param t the function argument
* @return the function result
*/
R apply(T t);

 Hello
llo

There are input parameters , There is a return value

 

4、 Assertion interface ：Predicate

（1） Functional interface

@FunctionalInterface
public interface Predicate<T> {
/**
* Evaluates this predicate on the given argument.
*
* @param t the input argument
* @return {@code true} if the input argument matches the predicate,
* otherwise {@code false}
*/
boolean test(T t);

（2） test

 public List<String> filterStr(List<String> list, Predicate<String> pre) {
List<String> strList = new ArrayList<>();
for (String str : list) {
if (pre.test(str)) {
strList.add(str);
}
}
return strList;
}
@Test
public void test4() {
List<String> list = Arrays.asList("Hello", "nihaoyyyy", "Lambda", "www", "ok");
List<String> strList = filterStr(list, (s) -> s.length() > 3);
for (String str : strList) {
System.out.println(str);
}
}

There's input , The return value is Boolean Type of

 

5、 Other interfaces

（1） Other interfaces