entityMap|blocks|key|a91d7|text|下面的示例将在编译时不会出错：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|8soo6|public+void+test()+{
++from(Customer.class).where(c+->+c.getAge()+>+20).select(Customer::getUserName);
}

public+<T>+Builder<T>+from(Class<T>+cls)+{
++return+new+Builder<>(cls);
}

public+class+Builder<T>+{
++private+Class<T>+cls;

++public+Builder(Class<T>+cls)+{
++++this.cls+=+cls;
++}

++public+Builder<T>+where(Predicate<T>+predicate)+{
++++//+store+predicate
++++return+this;
++}

++public+Builder<T>+select(Function<T,+Object>+field)+{
++++//+store+field+selector
++++return+this;
++}
}

public+class+Customer+{
++private+String+userName;
++private+int+age;

++public+int+getAge()+{
++++return+age;
++}

++public+String+getUserName()+{
++++return+userName;
++}
}|code-block|syntax|javascript|ekgq1|但是，您不能直接访问private字段，您需要为它们提供一个getter。|offset|length|style|CODE|2866a^0|0|0|A|7|0^^$0|$]|1|@$2|3|4|5|6|7|8|O|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|P|9|@]|A|@]|B|$F|G]]|$2|H|4|I|6|7|8|Q|9|@$J|R|K|S|L|M]]|A|@]|B|$]]|$2|N|4|-4|6|7|8|T|9|@]|A|@]|B|$]]]]

The example below will compile without error:

<pre><code>public void test() {
 from(Customer.class).where(c -&gt; c.getAge() &gt; 20).select(Customer::getUserName);
}

public &lt;T&gt; Builder&lt;T&gt; from(Class&lt;T&gt; cls) {
 return new Builder&lt;&gt;(cls);
}

public class Builder&lt;T&gt; {
 private Class&lt;T&gt; cls;

 public Builder(Class&lt;T&gt; cls) {
 this.cls = cls;
 }

 public Builder&lt;T&gt; where(Predicate&lt;T&gt; predicate) {
 // store predicate
 return this;
 }

 public Builder&lt;T&gt; select(Function&lt;T, Object&gt; field) {
 // store field selector
 return this;
 }
}

public class Customer {
 private String userName;
 private int age;

 public int getAge() {
 return age;
 }

 public String getUserName() {
 return userName;
 }
}
</code></pre>

You can't access <code>private</code> fields directly though, you need a getter for them.

entityMap|blocks|key|24jek|text|您可以使用流API来实现以下功能：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|d3ult|customers.stream().filter(customer+=>+customer.getAge()+>+20).map(Customer::getUserName).collect(Collectors.toList())|code-block|syntax|javascript|chrqo^0|0|0^^$0|$]|1|@$2|3|4|5|6|7|8|I|9|@]|A|@]|B|$]]|$2|C|4|D|6|E|8|J|9|@]|A|@]|B|$F|G]]|$2|H|4|-4|6|7|8|K|9|@]|A|@]|B|$]]]]

You can use stream API for this:

<pre><code>customers.stream().filter(customer =&gt; customer.getAge() &gt; 20).map(Customer::getUserName).collect(Collectors.toList())
</code></pre>

entityMap|0|type|LINK|mutability|MUTABLE|data|url|https://projectlombok.org/|1|https://github.com/timandy/linq|blocks|key|6vma1|text|我是Linq+to+Objects(Java)的作者。您可以使用lombok和Linq来实现这一点。|unstyled|depth|inlineStyleRanges|entityRanges|9ijpk|val+result+=+Linq.asEnumerable(customers).where(customer+->+customer.getAge()+>+20).select(customer+->+customer.getUserName());|code-block|syntax|javascript|d26ue|lombok|offset|length|af62r|Linq|o6su^0|0|0|0|6|0|0|0|4|1|0^^$0|$1|$2|3|4|5|6|$7|8]]|9|$2|3|4|5|6|$7|A]]]|B|@$C|D|E|F|2|G|H|W|I|@]|J|@]|6|$]]|$C|K|E|L|2|M|H|X|I|@]|J|@]|6|$N|O]]|$C|P|E|Q|2|G|H|Y|I|@]|J|@$R|Z|S|10|C|11]]|6|$]]|$C|T|E|U|2|G|H|12|I|@]|J|@$R|13|S|14|C|15]]|6|$]]|$C|V|E|-4|2|G|H|16|I|@]|J|@]|6|$]]]]

I'm the author of Linq to Objects(Java). You can use lombok and Linq to impl this.

<pre><code>val result = Linq.asEnumerable(customers).where(customer -&gt; customer.getAge() &gt; 20).select(customer -&gt; customer.getUserName());

</code></pre>

<a href="https://projectlombok.org/" rel="nofollow noreferrer">lombok</a>

<a href="https://github.com/timandy/linq" rel="nofollow noreferrer">Linq</a>

In C# we have the option to specify a property of an object using property selectors (for example when using LINQ) like so:

<pre><code>var usernames = customers.Where(x =&gt; x.Age &gt; 20).Select(x =&gt; x.Username);
</code></pre>

Here we first select the property <code>Age</code> to perform the comparison on and then specify the property <code>Username</code> to the <code>Select(...)</code> clause.

I am currently trying to replicate this functionality using lambda expressions in Java to enable users of my code to specify which property should be used for some action later on. The final result should look similar to the following:

<pre><code>public class Builder&lt;T&gt; {

// ...
private Field field;

Builder&lt;T&gt; forField(SomeFunctionalInterface s) {
 this.field = s.evaluate();
 return this;
 }
// ...
}
</code></pre>

Thank you for your effort.

Is there a way to simulate property selectors in java?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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 在C#中，我们可以选择使用属性选择器来指定对象的属性(例如，当使用LINQ时)，如下所示： var usernames = customers.Where(x => x.Age > 20).Select(x => x.Username); 在这里，我们首先选择要执行比较的属性Age，然后将属性Username指定给S...

问有没有办法在java中模拟属性选择器？
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问有没有办法在java中模拟属性选择器？EN