Java Generics 简明教程

Java Generics - Raw Types

如果在创建过程中没有传递类型参数，则原始类型是泛型类或接口的对象。以下示例將展示上述概念。

A raw type is an object of a generic class or interface if its type arguments are not passed during its creation. Following example will showcase above mentioned concept.

Example

使用任意你选择的编辑器创建以下 Java 程序。

Create the following java program using any editor of your choice.

GenericsTester.java

package com.tutorialspoint;

public class GenericsTester {
   public static void main(String[] args) {
      Box<Integer> box = new Box<Integer>();

      box.set(Integer.valueOf(10));
      System.out.printf("Integer Value :%d\n", box.getData());


      Box rawBox = new Box();

      //No warning
      rawBox = box;
      System.out.printf("Integer Value :%d\n", rawBox.getData());

      //Warning for unchecked invocation to set(T)
      rawBox.set(Integer.valueOf(10));
      System.out.printf("Integer Value :%d\n", rawBox.getData());

      //Warning for unchecked conversion
      box = rawBox;
      System.out.printf("Integer Value :%d\n", box.getData());
   }
}

class Box<T> {
   private T t;

   public void set(T t) {
      this.t = t;
   }

   public T getData() {
      return t;
   }
}

这将产生以下结果。

This will produce the following result.

Output

Integer Value :10
Integer Value :10
Integer Value :10
Integer Value :10