java 根据两个属性排序

Question

问题描述
有一个list集合，包含name，可空。date非空。现在需要排序。需要name是null的排在前面，然后按照date排序
问题出现的环境背景及自己尝试过哪些方法
list.sort();
相关代码
//请把代码文本粘贴到下方（请勿用图片代替代码）Listpeople=newArrayList<>();
people.add(newPerson(1,null,sdf.parse("2019-09-2312:12:12")));
people.add(newPerson(2,"1",sdf.parse("2019-09-2312:12:12")));
people.add(newPerson(3,null,sdf.parse("2019-09-2412:12:12")));
people.add(newPerson(4,"1",sdf.parse("2019-09-2412:12:12")));
people.add(newPerson(5,null,sdf.parse("2019-09-1712:12:12")));
people.add(newPerson(6,null,sdf.parse("2019-09-2412:12:12")));
people.add(newPerson(8,null,sdf.parse("2019-09-2012:12:12")));
people.add(newPerson(9,null,sdf.parse("2019-09-2312:12:12")));
people.add(newPerson(10,"1",sdf.parse("2019-09-2012:12:12")));
people.sort((t1,t2)->{
if(t1.getName()==null&&t2.getName()!=null){
return-1;
}elseif(t2.getName()==null&&t1.getName()!=null){
return-1;
}elseif(Objects.equals(t1.getName(),t2.getName())){
returnt1.getEntryDate().compareTo(t2.getEntryDate());
}else{
returnt1.getName().compareTo(t2.getName());
}
});
System.out.println("SORT===========================");
println(people);
你期待的结果是什么？实际看到的错误信息又是什么？
期望结果：Person[id=5,name=null,entryDate=2019-09-1712:12:12]Person[id=8,name=null,entryDate=2019-09-2012:12:12]Person[id=9,name=null,entryDate=2019-09-2312:12:12]Person[id=1,name=null,entryDate=2019-09-2312:12:12]Person[id=3,name=null,entryDate=2019-09-2412:12:12]Person[id=6,name=null,entryDate=2019-09-2412:12:12]Person[id=10,name=1,entryDate=2019-09-2012:12:12]Person[id=2,name=1,entryDate=2019-09-2312:12:12]Person[id=4,name=1,entryDate=2019-09-2412:12:12]输出结果：SORT===========================Person[id=10,name=1,entryDate=2019-09-2012:12:12]Person[id=5,name=null,entryDate=2019-09-1712:12:12]Person[id=8,name=null,entryDate=2019-09-2012:12:12]Person[id=9,name=null,entryDate=2019-09-2312:12:12]Person[id=4,name=1,entryDate=2019-09-2412:12:12]Person[id=3,name=null,entryDate=2019-09-2412:12:12]Person[id=2,name=1,entryDate=2019-09-2312:12:12]Person[id=1,name=null,entryDate=2019-09-2312:12:12]Person[id=6,name=null,entryDate=2019-09-2412:12:12]

Answer 1

elseif(t2.getName()==null&&t1.getName()!=null){return1;}第二个if与第一个相反的情况,返回值应该相反,否则顺序会乱