Java 8 流 - 或条件
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Java 8 stream - or condition
提问by Rockoder
See this code: (This is working code but I don't like to use 2 lines so looking for how can I make it better)
请参阅此代码：（这是工作代码，但我不喜欢使用 2 行，因此正在寻找如何使其更好）
ItemDetails[] items = response.getDetailsList();
items = Arrays.stream(items).filter(x -> !x.getName().equalsIgnoreCase("acl1")).toArray(ItemDetails[]::new);
items = Arrays.stream(items).filter(x -> !x.getName().equalsIgnoreCase("acl2")).toArray(ItemDetails[]::new);
I could not figure how to use an OR (|)condition within filterto remove two specific elements from Listsince it would give me compile time error (in IDE) and I end up using two filterslike above.
What could I be missing?
我无法弄清楚如何使用其中的OR (|)条件filter来从中删除两个特定元素，List因为它会给我编译时错误（在 IDE 中）并且我最终使用了filters上面的两个。我可能会错过什么？
This is how I tried to use OR
这就是我尝试使用 OR 的方式
items = Arrays.stream(items).filter(x -> !x.getName().equalsIgnoreCase("acl1") ||
x -> !x.getName().equalsIgnoreCase("acl2")).toArray(ItemDetails[]::new);
=> IntelliJ would complain about this one (above)
=> IntelliJ 会抱怨这个（上图）
items = Arrays.stream(items).filter(x -> !x.getName().equalsIgnoreCase("acl1"") ||
x.getName().equalsIgnoreCase("acl2")).toArray(ItemDetails[]::new);
Does not work at runtime (it does not filter)
在运行时不起作用（它不过滤）
Entire code with commented code (which I tried) for reference
带有注释代码（我尝试过）的整个代码以供参考
public static void mapTest () {
AclDetailItem[] items = new AclDetailItem[3];
AclDetailItem item1 = new AclDetailItem();
item1.setAclName("acl1");
AclDetailItem item2 = new AclDetailItem();
item2.setAclName("acl2");
AclDetailItem item3 = new AclDetailItem();
item3.setAclName("acl3");
items[0] = item1;
items[1] = item2;
items[2] = item3;
System.out.println ("Before " + items.length);
items = Arrays.stream(items).filter(x -> !x.getAclName().equalsIgnoreCase("acl1")).toArray(ItemDetails[]::new);
items = Arrays.stream(items).filter(x -> !x.getAclName().equalsIgnoreCase("acl2")).toArray(ItemDetails[]::new);
System.out.println ("After " + items.length);
}
回答by krmanish007
You should create multiple predicates for each condition and join it using or. I have added my below example:
您应该为每个条件创建多个谓词并使用 or 连接它。我添加了以下示例：
public class MeTest {
Predicate<Integer> con1 = i -> i==0;
Predicate<Integer> con2 = i -> i==1;
Predicate<Integer> con3 = i -> i==2;
@Test
public void testOr() {
List<Integer> asdas = IntStream.range(1, 10).boxed().filter(con1.or(con2).or(con3)).collect(toList());
System.out.println("asdas = " + asdas);
}
}
回答by Roland
The first one is incorrect as it has a x ->too much.
The second one does not filter as you constructed a condition that is always true. Just refine your condition in the filter-method and it will filter.
第一个不正确，因为它有x ->太多。第二个不会过滤，因为您构建了一个始终为 的条件true。只需在filter-method 中优化您的条件，它就会进行过滤。
EDIT (as the question got detailed):
I still think, you have an error in your condition. You probably want to exclude both acl1and acl2. If so, your condition should rather look something like:
编辑（随着问题的详细化）：我仍然认为，您的情况有误。您可能想同时排除acl1和acl2。如果是这样，您的情况应该类似于：
!(x.getAclName().equalsIgnoreCase("acl1") || x.getAclName().equalsIgnoreCase("acl2"))
// or if you prefer &&
!x.getAclName().equalsIgnoreCase("acl1") && !x.getAclName().equalsIgnoreCase("acl2")
// or if you prefer regular expressions/matches
!x.getAclName().matches("(?i)^acl[1|2]$")
回答by Carcigenicate
items = Arrays.stream(items).filter(
x -> !x.getName().equalsIgnoreCase("redirect")
|| x->!x.getName().equalsIgnoreCase("success"))
.toArray(ItemDetails[]::new);
Note the second x->. That's used to bind a variable at the start of a lambda. Putting it in the middle is invalid, and unnecessary since xalready exists in the scope. Just remove that bit:
注意第二个x->。这用于在 lambda 的开头绑定一个变量。把它放在中间是无效的，而且没有必要，因为它x已经存在于作用域中。只需删除那一点：
items = Arrays.stream(items).filter(x ->
!x.getName().equalsIgnoreCase("redirect")
|| !x.getName().equalsIgnoreCase("success"))
.toArray(ItemDetails[]::new);
