Java流筛选器空指针问题

Question

我有以下信息流：

services = services.stream()
        .filter(service -> (service.getType().isEmpty() || service.getType().equals(type)))
        .collect(Collectors.toList());

其中service.type是字符串，type也是字符串。我的筛选器应该返回所有服务，其type等于null（或者干脆为空），或者返回给定类型

这给我带来了一个错误：

java.lang.NullPointerException: null at com.eternity.service.OrderService.lambda$getServicesForOrder$0(OrderService.java:140) ~[classes/:na] at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174) ~[na:1.8.0_77] at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374) ~[na:1.8.0_77] at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) ~[na:1.8.0_77] at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) ~[na:1.8.0_77] at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[na:1.8.0_77] at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_77] at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[na:1.8.0_77] at com.eternity.service.OrderService.getServicesForOrder(OrderService.java:141) ~[classes/:na]

我错过了什么

Answer 1

问题是：我在空对象上使用了.isEmpty()。我不得不使用StringUtils.isEmpty()方法：

services = services.stream()
        .filter(service -> (StringUtils.isEmpty(service.getType()) || service.getType().equals(type)))
        .collect(Collectors.toList());