Stream系列（五）Min Max Average方法使用

最小值，最大值，平均值
EmployeeTestCase.java

package com.example.demo;

import lombok.Data;
import lombok.ToString;
import lombok.extern.log4j.Log4j2;
import org.junit.Test;

import java.util.Collection;
import java.util.Comparator;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.LongStream;
import java.util.stream.Stream;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

@Log4j2
public class EmployeeTestCase extends BaseTest{
    @Test
    public void minMaxAverage() {
        Employee employeeMaX = list.stream().max(Comparator.comparing(Employee::getSalary)).orElse(null);
        assertEquals("Michael",employeeMaX.getName());
        Employee employeeMin = list.stream().min(Comparator.comparing(Employee::getSalary)).orElse(null);
        assertEquals("Alex",employeeMin.getName());
        double dMax = list.stream().mapToDouble(e -> e.getSalary()).max().orElse(0.00);
        assertTrue(dMax == 2000);
        double dMin = list.stream().mapToDouble(e -> e.getSalary()).min().orElse(0.00);
        assertTrue(dMin == 1000);
        double dAverage = list.stream().mapToDouble(e -> e.getSalary()).average().orElse(0.00);
        log.info("dAverage:{}",dAverage);
    }
}

BaseTest.java

package com.example.demo;

import java.util.Arrays;
import java.util.List;

public class BaseTest {
    protected static final List<Employee> list = Arrays.asList(
            new Employee(1, "Alex", 1000),
            new Employee(2, "Michael", 2000),
            new Employee(3, "Jack", 1500),
            new Employee(4, "Owen", 1500),
            new Employee(5, "Denny", 2000));

    protected static final List<List<Employee>> listFlat = Arrays.asList(
            Arrays.asList(new Employee(1, "Alex", 1000),
                    new Employee(2, "Michael", 2000)),
            Arrays.asList(new Employee(3, "Jack", 1500),
                    new Employee(4, "Owen", 1500)),
            Arrays.asList(new Employee(5, "Denny", 2000)));
}

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