instanceof、isInstance、isAssignableFrom的区别

发布时间：2020-12-14 06:23:14 所属栏目：Java 来源：网络整理

导读：https://stackoverflow.com/questions/3949260/java-class-isinstance-vs-class-isassignablefrom 1. MyClass.class.isInstance(obj) ?is for checking an instance. It returns true when the parameter obj is non-null and can be cast to? MyClass ?with

https://stackoverflow.com/questions/3949260/java-class-isinstance-vs-class-isassignablefrom

1. MyClass.class.isInstance(obj)?is for checking an instance. It returns true when the parameter obj is non-null and can be cast to?MyClass?without raising a?ClassCastException. In other words,obj is an instance of?MyClass?or its subclasses.

2.?MyClass.class.isAssignableFrom(Other.class)?will return true if?MyClass?is the same as,or a superclass or superinterface of,?Other.?Other?can be a class or an interface. It answers true if?Other?can be converted to a?MyClass.

</span><span style="color: #0000ff;"&gt;public</span> <span style="color: #0000ff;"&gt;void</span><span style="color: #000000;"&gt; doit()
{
    A myA </span>= <span style="color: #0000ff;"&gt;new</span><span style="color: #000000;"&gt; A();
    B myB </span>= <span style="color: #0000ff;"&gt;new</span><span style="color: #000000;"&gt; B();
    A[] aArr </span>= <span style="color: #0000ff;"&gt;new</span> A[0<span style="color: #000000;"&gt;];
    B[] bArr </span>= <span style="color: #0000ff;"&gt;new</span> B[0<span style="color: #000000;"&gt;];

    System.out.println(</span>"b instanceof a: " + (myB <span style="color: #0000ff;"&gt;instanceof</span><span style="color: #000000;"&gt; A));
    System.out.println(</span>"b isInstance a: " + A.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;.isInstance(myB));
    System.out.println(</span>"a isInstance b: " + B.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;.isInstance(myA));
    System.out.println(</span>"b isAssignableFrom a: " + A.<span style="color: #0000ff;"&gt;class</span>.isAssignableFrom(B.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;));
    System.out.println(</span>"a isAssignableFrom b: " + B.<span style="color: #0000ff;"&gt;class</span>.isAssignableFrom(A.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;));
    System.out.println(</span>"bArr isInstance A: " + A.<span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt;.isInstance(bArr));
    System.out.println(</span>"bArr isInstance aArr: " +<span style="color: #000000;"&gt; aArr.getClass().isInstance(bArr));
    System.out.println(</span>"bArr isAssignableFrom aArr: " +<span style="color: #000000;"&gt; aArr.getClass().isAssignableFrom(bArr.getClass()));
}

</span><span style="color: #0000ff;"&gt;class</span><span style="color: #000000;"&gt; A
{
}

</span><span style="color: #0000ff;"&gt;class</span> B <span style="color: #0000ff;"&gt;extends</span><span style="color: #000000;"&gt; A
{
}

}

结果

b a:

（编辑：李大同）

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