JAVA运算符 instanceof
2016-06-01 14:44
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判断对象object是否为指定类class的实例
例
当是指定类实例时返回 true
当不是指定类实例或者object 为null 时返回 false
测试代码
例
boolean result = object instanceof class
当是指定类实例时返回 true
当不是指定类实例或者object 为null 时返回 false
测试代码
interface A{} class B implements A{ } class C extends B { } class instanceoftest { public static void main(String[] args){ A a=null; B b=null; boolean res; System.out.println("instanceoftest test case 1: ------------------"); res = a instanceof A; System.out.println("a instanceof A: " + res); res = b instanceof B; System.out.println("b instanceof B: " + res); System.out.println("/ninstanceoftest test case 2: ------------------"); a=new B(); b=new B(); res = a instanceof A; System.out.println("a instanceof A: " + res); res = a instanceof B; System.out.println("a instanceof B: " + res); res = b instanceof A; System.out.println("b instanceof A: " + res); res = b instanceof B; System.out.println("b instanceof B: " + res); System.out.println("/ninstanceoftest test case 3: ------------------"); B b2=(C)new C(); res = b2 instanceof A; System.out.println("b2 instanceof A: " + res); res = b2 instanceof B; System.out.println("b2 instanceof B: " + res); res = b2 instanceof C; System.out.println("b2 instanceof C: " + res); } } /* result: instanceoftest test case 1: ------------------ a instanceof A: false b instanceof B: false instanceoftest test case 2: ------------------ a instanceof A: true a instanceof B: true b instanceof A: true b instanceof B: true instanceoftest test case 3: ------------------ b2 instanceof A: true b2 instanceof B: true b2 instanceof C: true */
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