java - 使用 <this.class> 实例化通用字段

Question

我有以下代码

public class ComplicatedBuilder extends MyBuilder
{
  public final Parameter<ComplicatedBuilder, Long> par1 = new Parameter<>(this);
  public final Parameter<ComplicatedBuilder, Long> par2 = new Parameter<>(this);
  ...
}

public class Parameter<B extends MyBuilder, T>
{
  private T val;
  private B builder;
  public Parameter(B b)
  {
    builder = b;
  }

  public B setValue(T v)
  {
    val = v;
    return builder;
  }
  ...
}

//usage:
ComplicatedBuilder builder = new ComplicatedBuilder();
builder
  .par1.setValue(5)
  .par2.setValue(7);

我如何声明参数像 public final Parameter<this.class, Long> par1 ... ？我想以允许将参数列表复制粘贴到另一个构建器而无需进行大量更改的方式来执行此操作。

Answer 1

你是这个意思吗？

abstract class AbstractComplicatedBuilder<B extends AbstractComplicatedBuilder<B>> 
                         extends MyBuilder {
    public final Parameter<B, Long> par1 = new Parameter<>(self());
    public final Parameter<B, Long> par2 = new Parameter<>(self());

    abstract B self();
}

class ComplicatedBuilder extends AbstractComplicatedBuilder<ComplicatedBuilder>{
    ComplicatedBuilder self(){
        return this;
    }
}

您可以推迟实际的 AbstractComplicatedBuilder使用通用参数 B extends AbstractComplicatedBuilder<B> 进行构建.