Lambda表达式的四大内置核心函数式接口

1、消费型接口

package com.zh.lambda;

import java.util.function.Consumer;
import org.junit.Test;

/**
 * @desc Consumer<T>消费型接口
 * @author zhanh247
 */
public class ConsumerTest {

    @Test
    public void test() {
        happy(10000d, (x) -> System.out.println(x));
    }

    private void happy(Double money, Consumer<Double> consumer) {
        consumer.accept(money);
    }

}

2、供给型接口

package com.zh.lambda;

import java.util.ArrayList;
import java.util.List;
import java.util.function.Supplier;
import org.junit.Test;

/**
 * @desc Supplier<T>供给型接口
 * @author zhanh247
 */
public class SupplierTest {

    @Test
    public void test() {
        List<Integer> nums = getNums(10, () -> (int) (Math.random() * 100));
        for (Integer integer : nums) {
            System.out.println(integer);
        }
    }

    private List<Integer> getNums(Integer num, Supplier<Integer> supplier) {
        List<Integer> numList = new ArrayList<Integer>();
        for (int i = 0; i < num; i++) {
            Integer n = supplier.get();
            numList.add(n);
        }
        return numList;
    }

}

3、断言型接口

package com.zh.lambda;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
import org.junit.Test;

/**
 * @desc Predicate<T>断言型接口
 * @author zhanh247
 */
public class PredicateTest {

    @Test
    public void test() {
        List<String> strLists = Arrays.asList("asdfasdf", "cccc", "hello world!", "ddd", "22", "www", "ok");
        List<String> filterStr = filterStr(strLists, (x) -> x.length() > 5);
        for (String str : filterStr) {
            System.out.println(str);
        }
    }

    private List<String> filterStr(List<String> strLists, Predicate<String> predicate) {
        List<String> lists = new ArrayList<String>();
        for (String str : strLists) {
            if (predicate.test(str)) {
                lists.add(str);
            }
        }
        return lists;
    }
}

4、函数式接口

package com.zh.lambda;

import java.util.function.Function;
import org.junit.Test;

/**
 * @desc Function<T,R>函数式接口
 * @author zhanh247
 */
public class FunctionTest {

    @Test
    public void test() {
        String str = strHandle("asdfasdfasedf", (x) -> x.substring(3, 5));
        System.out.println(str);
    }

    private String strHandle(String str, Function<String, String> function) {
        return function.apply(str);
    }

}

5、方法引用

package com.zh.lambda.ref;

import java.util.Comparator;
import java.util.function.BiFunction;
import java.util.function.BiPredicate;
import java.util.function.Function;
import java.util.function.Supplier;
import org.junit.Test;

/**
 * @desc 方法引用
 * @author zhanh247
 */
public class LambdaRefTest {

    @Test
    public void test() {
        // 1、对象：实例方法名
        Employee employee = new Employee();
        Supplier<String> supplier = () -> employee.getName();
        String string = supplier.get();
        System.out.println(string);

        Supplier<Integer> supplier2 = employee::getAge;
        Integer string2 = supplier2.get();
        System.out.println(string2);

        // 2、静态方法名
        Comparator<Integer> com1 = (x, y) -> Integer.compare(x, y);
        Comparator<Integer> com2 = Integer::compare;

        // 3、类:实例方法名
        BiPredicate<String, String> bp1 = (x, y) -> x.equals(y);
        BiPredicate<String, String> bp2 = String::equals;

        // 4、构造器引用
        Supplier<Employee> su1 = () -> new Employee();
        Supplier<Employee> su2 = Employee::new;

        Function<Integer, Employee> fu1 = (x) -> new Employee(x);
        Function<Integer, Employee> fu2 = Employee::new;

        BiFunction<Integer, String, Employee> bf1 = (x, y) -> new Employee(x, y);
        BiFunction<Integer, String, Employee> bf2 = Employee::new;
        Employee apply = bf2.apply(10, "hello");
        System.out.println(apply);

        // 5、数组引用
        Function<Integer, String[]> func1 = (x) -> new String[x];
        String[] apply1 = func1.apply(10);
        System.out.println(apply1.length);

        Function<Integer, String[]> func2 = String[]::new;
        String[] apply2 = func2.apply(20);
        System.out.println(apply2.length);

    }

}

6、实体类

package com.zh.lambda.ref;

public class Employee {

    private Integer age;
    private String name;
    private double salary;

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public Employee() {

    }

    public Employee(Integer age) {
        this.age = age;
    }

    public Employee(Integer age, String name) {
        this.age = age;
        this.name = name;
    }

    public Employee(Integer age, String name, double salary) {
        this.age = age;
        this.name = name;
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "Employee [age=" + age + ", name=" + name + ", salary=" + salary + "]";
    }

}