使用Java8

Question

我想将对象列表转换为Map，
我尝试使用Java 8的流API来实现它 我收到2个错误，1个导入，1个转换代码为List to Map。

导入Map界面时出错 -
The import java.util.Map conflicts with a type defined in the same file.

转换代码错误 -

The type Map is not generic; it cannot be parameterized with arguments <String, BigDecimal>

以下是我的代码 -

public class Developer {

    private String name;
    private BigDecimal sal;
    private int age;

    /**
     * @param name
     * @param sal
     * @param age
     */
    public Developer(String name, BigDecimal sal, int age) {
        super();
        this.name = name;
        this.sal = sal;
        this.age = age;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name
     *            the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the sal
     */
    public BigDecimal getSal() {
        return sal;
    }

    /**
     * @param sal
     *            the sal to set
     */
    public void setSal(BigDecimal sal) {
        this.sal = sal;
    }

    /**
     * @return the age
     */
    public int getAge() {
        return age;
    }

    /**
     * @param age
     *            the age to set
     */
    public void setAge(int age) {
        this.age = age;
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "Developer [name=" + name + ", sal=" + sal + ", age=" + age + "]";
    }

}

我的主要课程 -

import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.Map;

public class Map {

    public static void main(String[] args) {

        List<Developer> listDevs = getDevelopers();

        //Error here
        Map<String, BigDecimal> result =  listDevs.stream().collect(Collectors.toMap(Developer :: getName, Developer :: getSal));

    }

    private static List<Developer> getDevelopers() {

        List<Developer> result = new ArrayList<>();

        result.add(new Developer("mkyong", new BigDecimal("70000"), 33));
        result.add(new Developer("alvin", new BigDecimal("80000"), 20));
        result.add(new Developer("jason", new BigDecimal("100000"), 10));
        result.add(new Developer("iris", new BigDecimal("170000"), 55));

        return result;

    }
}

我提到了以下问题，但我无法导入Map界面 - The type HashMap is not generic; it cannot be parameterized with arguments <String, Integer>

Answer 1

包含类称为Map，因此编译错误。要解决此问题，只需将您的类重命名为其他名称或使用：

java.util.Map<String, BigDecimal> result =  
        listDevs.stream()
                .collect(Collectors.toMap(Developer::getName, Developer::getSal));

Answer 2

除了更改类名，您还可以执行以下操作：

java.util.Map<String, BigDecimal> result = listDevs.stream().collect(Collectors.toMap(Developer::getName, Developer::getSal));