Java中Type接口与Class类的区别联系

1.Type定义与说明

源代码：

package java.lang.reflect;

/**
 * Type is the common superinterface for all types in the Java
 * programming language. These include raw types, parameterized types,
 * array types, type variables and primitive types.
 *
 * @since 1.5
 */
public interface Type {
    /**
     * Returns a string describing this type, including information
     * about any type parameters.
     *
     * @implSpec The default implementation calls {@code toString}.
     *
     * @return a string describing this type
     * @since 1.8
     */
    default String getTypeName() {
        return toString();
    }
}

总结来说：

• Type是一个接口。
• Type是Java中所有类型的父接口。
• Type包括：raw type(原始类型，对应Class),parameterized types(参数化类型), array types(数组类型), type variables(类型变量) and primitive types(基本类型，对应Class).
• Type是JDK1.5引入的，主要是为了泛型。

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2.Class定义与说明

源代码：

/**
 * Instances of the class {@code Class} represent classes and
 * interfaces in a running Java application.  An enum is a kind of
 * class and an annotation is a kind of interface.  Every array also
 * belongs to a class that is reflected as a {@code Class} object
 * that is shared by all arrays with the same element type and number
 * of dimensions.  The primitive Java types ({@code boolean},
 * {@code byte}, {@code char}, {@code short},
 * {@code int}, {@code long}, {@code float}, and
 * {@code double}), and the keyword {@code void} are also
 * represented as {@code Class} objects.
 *
 * 
 {@code Class} has no public constructor. Instead {@code Class}
 * objects are constructed automatically by the Java Virtual Machine as classes
 * are loaded and by calls to the {@code defineClass} method in the class
 * loader.
 *
 * 
 The following example uses a {@code Class} object to print the
 * class name of an object:
 *
 * 
 *     void printClassName(Object obj) {
 *         System.out.println("The class of " + obj +
 *                            " is " + obj.getClass().getName());
 *     }
 * 
 *
 * 
 It is also possible to get the {@code Class} object for a named
 * type (or for void) using a class literal.  See Section 15.8.2 of
 * The Java™ Language Specification.
 * For example:
 *
 * 

 *     {@code System.out.println("The name of class Foo is: "+Foo.class.getName());}
 * 
 *
 * @param  the type of the class modeled by this {@code Class}
 * object.  For example, the type of {@code String.class} is {@code
 * Class}.  Use {@code Class} if the class being modeled is
 * unknown.
 *
 * @author  unascribed
 * @see     java.lang.ClassLoader#defineClass(byte[], int, int)
 * @since   JDK1.0
 */
public final class Class<T> implements java.io.Serializable,
                              GenericDeclaration,
                              Type,
                              AnnotatedElement {
}

总结来说：

• Class是一个类。
• Class对象代表着正在运行的Java程序中的类型和接口：enum、annotation、array以及基本类型(8种)都可以用Class对象表示。
• Class没有public构造器。
• 当类被加载或者在class loader中被方法调用时，JVM会自动构造Class对象。

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3.Type接口与Class类的区别联系

• Type是Class的父接口。
• Class是Type的子类。