无法推断功能接口类型 Java 8
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Cannot infer functional interface type Java 8
提问by user3407267
I have a factory(Registry DP) which initializes the class:
我有一个初始化类的工厂（注册表 DP）：
public class GenericFactory extends AbstractFactory {
public GenericPostProcessorFactory() {
factory.put("Test",
defaultSupplier(() -> new Test()));
factory.put("TestWithArgs",
defaultSupplier(() -> new TestWithArgs(2,4)));
}
}
interface Validation
Test implements Validation
TestWithArgs implements Validation
And in the AbstractFactory
在抽象工厂中
protected Supplier<Validation> defaultSupplier(Class<? extends Validation> validationClass) {
return () -> {
try {
return validationClass.newInstance();
} catch (InstantiationException | IllegalAccessException e) {
throw new RuntimeException("Unable to create instance of " + validationClass, e);
}
};
}
But I keep getting Cannot infer functional interface type Error. What I am doing wrong here ?
但我不断收到无法推断功能接口类型错误。我在这里做错了什么？
采纳答案by Holger
Your defaultSuppliermethod has an argument type of Class. You can't pass a lambda expression where a Classis expected. But you don't need that method defaultSupplieranyway.
您的defaultSupplier方法的参数类型为Class. 您不能在需要 a 的地方传递 lambda 表达式Class。但defaultSupplier无论如何你都不需要那种方法。
Since Testand TestWithArgsare a subtypes of Validation, the lambda expressions () -> new Test()and () -> new TestWithArgs(2,4)are already assignable to Supplier<Validation>without that method:
由于Test和TestWithArgs是 的子类型Validation，因此 lambda 表达式() -> new Test()和() -> new TestWithArgs(2,4)已经可以在Supplier<Validation>没有该方法的情况下分配给：
public class GenericFactory extends AbstractFactory {
public GenericPostProcessorFactory() {
factory.put("Test", () -> new Test());
factory.put("TestWithArgs", () -> new TestWithArgs(2,4));
}
}
