我尝试将以下代码编写为流:
AbstractDevice myDevice = null;
for (AbstractDevice device : session.getWorkplace().getDevices()) {
if (device.getPluginconfig().getPluginType().getId() == 1) {
myDevice = device;
}
}
这段代码工作正常。
但是当我像这样重写它时,它不再起作用:
myDevice = session.getWorkplace().getDevices().stream()
.filter(s -> s.getPluginconfig().getPluginType().getId() == 1)
.findFirst().get();
The Optional
我从流中返回的内容没有任何值。为什么?
EDIT
当我尝试这个时(我仍然从getDevices()
):
List<AbstractDevice> testList = session.getWorkplace().getDevices()
.stream().collect(Collectors.toList());
the testList
是空的。所以我的流似乎出了问题List
设备数量?
这是一个 JavaEE 应用程序,我从相应的实体获取我的设备:
@ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH})
@JoinTable(name = "Workplace_AbstractDevice",
joinColumns = {
@JoinColumn(name = "Workplace", referencedColumnName = "ID")
},
inverseJoinColumns = {
@JoinColumn(name = "AbstractDevice", referencedColumnName = "ID")
})
@OrderColumn
private List<AbstractDevice> devices = new ArrayList<AbstractDevice>();
public List<AbstractDevice> getDevices() {
return devices;
}