Stream系列（九）Collector方法使用

toMap toList toCollection joining

視頻講解:https://www.bilibili.com/video/av77800638/

EmployeeTestCase.java

package com.example.demo;

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

import java.io.IOException;
import java.io.PrintWriter;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Vector;
import java.util.stream.Collectors;
import java.util.stream.Stream;

@Log4j2
public class EmployeeTestCase extends BaseTestCase {
    @Test
    public void collector() {
        //轉換成連接字符串
        String strName = list.stream().map(Employee::getName).collect(Collectors.joining(","));
        log.info("strName:{}", strName);
        //轉換成Set集合
        Set<String> setName = list.stream().map(Employee::getName).collect(Collectors.toSet());
        log.info("setName:{}", strName);
        //轉換成Vector
        Vector<String> vectorName = list.stream().map(Employee::getName).collect(Collectors.toCollection(Vector::new));
        //轉換成List
        List<String> listName = list.stream().map(Employee::getName).collect(Collectors.toList());
        //轉換成Map
        Map<Long, String> mapName = list.stream().collect(Collectors.toMap(employee -> employee.getId(), employee -> employee.getName()));
    }
}

BaseTestCase.java

package com.example.demo;

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

public class BaseTestCase {
    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));

}

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