java stream实现inner join

以下是Java Stream实现Inner Join的示例代码：

import java.util.*;
import java.util.stream.*;

public class InnerJoinExample {
    public static void main(String[] args) {
        // 创建左表
        List<Map<String, Object>> leftTable = new ArrayList<>();
        Map<String, Object> leftRow1 = new HashMap<>();
        leftRow1.put("id", 1);
        leftRow1.put("name", "Alice");
        leftTable.add(leftRow1);
        Map<String, Object> leftRow2 = new HashMap<>();
        leftRow2.put("id", 2);
        leftRow2.put("name", "Bob");
        leftTable.add(leftRow2);

        // 创建右表
        List<Map<String, Object>> rightTable = new ArrayList<>();
        Map<String, Object> rightRow1 = new HashMap<>();
        rightRow1.put("id", 1);
        rightRow1.put("age", 20);
        rightTable.add(rightRow1);
        Map<String, Object> rightRow2 = new HashMap<>();
        rightRow2.put("id", 3);
        rightRow2.put("age", 30);
        rightTable.add(rightRow2);

        // 定义连接条件
        String joinColumnTableLeft = "id";
        String joinColumnTableRight = "id";

        // 执行内连接
        List<Map<String, Object>> result = leftTable.stream()
                .flatMap(l -> rightTable.stream()
                        .filter(r -> Objects.equals(l.get(joinColumnTableLeft), r.get(joinColumnTableRight)))
                        .map(r -> {
                            Map<String, Object> row = new HashMap<>();
                            row.putAll(l);
                            row.putAll(r);
                            return row;
                        }))
                .collect(Collectors.toList());

        // 输出结果
        System.out.println(result);
    }
}