class.isAssignableFrom

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instanceof 针对实例
isAssignableFrom针对class对象

isAssignableFrom 是用来判断一个类Class1和另一个类Class2是否相同或是另一个类的超类或接口。
通常调用格式是

Java代码  

Class1.isAssignableFrom(Class2)

public boolean isAssignableFrom(Class<?> c) {    if (this == c) {        return true;  // Can always assign to things of the same type.    } else if (this == Object.class) {        return !c.isPrimitive();  // Can assign any reference to java.lang.Object.    } else if (isArray()) {        return c.isArray() && componentType.isAssignableFrom(c.componentType);    } else if (isInterface()) {        // Search iftable which has a flattened and uniqued list of interfaces.        Object[] iftable = c.ifTable;        if (iftable != null) {            for (int i = 0; i < iftable.length; i += 2) {                Class<?> ifc = (Class<?>) iftable[i];                if (ifc == this) {                    return true;                }            }        }        return false;    } else {        if (!c.isInterface()) {            for (c = c.superClass; c != null; c = c.superClass) {                if (c == this) {                    return true;                }            }        }        return false;    }}

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