Question

在班级7-b147的open-jdk com.sun.tools.javac.code.Type中，我们有以下方法

public boolean isCompound(){
    return tsym.completer==null
    // Compound types can't have a completer.  Calling
    // flags() will complete the symbol causing the
    // compiler to load classes unnecessarily.  This led
    // to regression 6180021.
    && (tsym.flags() & COMPOUND)!=0;

}

Java中的复合类型是什么意思？

Answer 1

在Google上进行研究，它们似乎是学术上提出的Java扩展“。

“复合类型”被描述为必须实现多个类或接口的引用类型的说明符。这是为了帮助静态验证＆amp;必须全部实现多个API（接口）时的编译时正确性。

发明的例子：

[CustomerService,IRpcGateway,IOSGiComponent] custSvc = new CustomerService();

我找到了以下链接：

Answer 2

Type.java中的TypeVar类具有以下注释，我认为很好地解释了COMPOUND类型的作用：

    /** The bound of this type variable; set from outside.
     *  Must be nonempty once it is set.
     *  For a bound, `bound' is the bound type itself.
     *  Multiple bounds are expressed as a single class type which has the
     *  individual bounds as superclass, respectively interfaces.
     *  The class type then has as `tsym' a compiler generated class `c',
     *  which has a flag COMPOUND and whose owner is the type variable
     *  itself. Furthermore, the erasure_field of the class
     *  points to the first class or interface bound.
     */

正如上面已经提到的，COMPOUND类型似乎模拟了由多个接口组成的类型变量的绑定类型，如：

class Example<T extends List<T> & Serializable>

java中的复合类型

2 个答案: