我不熟悉“泛型”。它是“<T extends SuperClass>
”的正确用法吗?您是否同意使用泛型后的代码更好?
Before using Generics
=================================================
public abstract class SuperSample {
public void getSomething(boolean isProcessA) {
doProcessX();
if(isProcessA){
doProcessY(new SubASample());
}else{
doProcessY(new SubBSample());
}
}
protected abstract void doProcessX();
protected void doProcessY(SubASample subASample) {
// Nothing to do
}
protected void doProcessY(SubBSample subBSample) {
// Nothing to do
}
}
public class SubASample extends SuperSample {
@Override
protected void doProcessX() {
System.out.println("doProcessX in SubASample");
}
@Override
protected void doProcessY(SubASample subASample) {
System.out.println("doProcessY in SubASample");
}
}
public class Sample {
public static void main(String[] args) {
SubASample subASample = new SubASample();
subASample.getSomething(true);
}
}
After using Generics
=================================================
public abstract class SuperSample {
public void getSomething(boolean isProcessA) {
doProcessX();
if(isProcessA){
doProcessY(new SubASample());
}else{
doProcessY(new SubBSample());
}
}
protected abstract void doProcessX();
protected abstract <T extends SuperSample> void doProcessY(T subSample);
}
public class SubASample extends SuperSample {
@Override
protected void doProcessX() {
System.out.println("doProcessX in SubASample");
}
@Override
protected <T extends SuperSample> void doProcessY(T subSample) {
System.out.println("doProcessY in SubASample");
}
}
public class Sample {
public static void main(String[] args) {
SubASample subASample = new SubASample();
subASample.getSomething(true);
}
}
最佳答案
如果你想做我认为你想做的事情,我认为这不是正确的方式(*)。如果你希望每个子类都需要实现一个方法来处理它自己的类型,那么你可以使用 CRTP 技巧:
abstract class Super<S extends Super<S>> {
abstract void process(S s);
}
class SubA extends Super<SubA> {
void process(SubA s){ /* do something */ }
}
class SubB extends Super<SubB> {
void process(SubB s){ /* do something */ }
}
请注意,此模式强制执行子类的通用签名,例如
class SubA extends Super<SubB>
无法编译。顺便说一下,Java 本身在
java.lang.Enum
中使用了这个技巧。(*)如果这不是您想要强制执行的行为,请说明。
关于java - "<T extends SuperClass>"的正确用法,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/5030578/