方式如下：
@Data
public class C {
private String name;
}
@Data
public class B {
private List cList;
}
@Data
public class A {
private String name;
private List bList;
}
public class Test {
public static void main(String[] args) {
A a1 = new A("a1");
A a2 = new A("a2");
A a3 = new A("a3");
// 具体的list数据准备，此处省略
......
List aList = Lists.newArrayList(a1, a2, a3);
// 筛选出A.name="a1", C对象的name属性。
List nameList = Optional.ofNullable(aList).orElse(Lists.newArrayList()).stream()
.filter(a -> Objects.equals("a1", a.getName())).flatMap(a -> a.getBList().stream())
.flatMap(b -> b.getCList().stream()).map(C::getName).collect(Collectors.toList());
// 代码纯手写，没有编译或者跑一下，若有问题，需自己改下。
}
}
按某种属性分类
@Data
public class B {
private String bName;
private String bCode;
private String bizType;
}
@Data
public class A {
private String aName;
private String aCode;
private List bList;
}
public class Test() {
public static void main(String[] args) {
A a = new A();
// 根据bizType对B对象分类
Map> resultMap = a.getBList().stream().collect(Collectors.groupingBy(B::getBizType))
}
}
