Java接口通用类型 [英] Java interface generic type

问题描述

接口：

  public interface TestInterface< E> {
 public void doSomething（E elem）; 
 
  

Class：

  public class TestClass implements TestInterface< E> {
 public static void main（）{
 // ... 
} 
 public void doSomething（E elem）{
 // ... 
} 
} 
  

当我运行javac编译器时。我得到这些错误：

  TestClass.java:5：找不到符号
符号：class E 
公共类TestClass实现TestInterface< E> {
 ^ 
 TestClass.java:11：找不到符号
符号：class E 
 location：class TestClass 
 public void doSomething（E elem）{
 ^ 
  

如果我用ieString替换所有的E ，但我希望它使用泛型类型。如何做到这一点？

解决方案

创建 TestClass 时，您需要传递 E ，如下所示

  public class TestClass implements TestInterface< ;字符串> {
 public static void main（）{
 // ... 
 
} 
 public void doSomething（String elem）{
 // .. 。
} 
} 
  

或者您需要制作 TestClass as generic

  public class TestClass< E>实现TestInterface< E> {
 public static void main（）{
 // ... 
 
} 
 public void doSomething（E elem）{
 // .. 。
} 
} 
  

Never used Java before and trying to implement an interface in a class:

Interface:

public interface TestInterface<E> {
        public void doSomething(E elem);
}

Class:

public class TestClass implements TestInterface<E> {
    public static void main() {
        // ...
    }
    public void doSomething(E elem) {
        // ...
    }
}

When I run the javac compiler. I get these errors:

TestClass.java:5: cannot find symbol
symbol: class E
      public class TestClass implements TestInterface<E> {
                                                      ^
TestClass.java:11: cannot find symbol
symbol  : class E
location: class TestClass
      public void doSomething(E elem) {
                              ^

If I replace all the "E"'s with i.e. "String", it will work, but I want it to use generic types. How do I do this?

解决方案

When creating TestClass you need to pass what is E, something like below

public class TestClass implements TestInterface<String> {
    public static void main() {
        // ...

    }
    public void doSomething(String elem) {
        // ...
    }
}

or you need to make TestClass as generic

public class TestClass<E> implements TestInterface<E> {
     public static void main() {
            // ...

     }
     public void doSomething(E elem) {
            // ...
     }
}

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