[size=1em]1 [size=1em]2 | [size=1em][size=1em]Object obj = NULL; // Not Ok [size=1em]Object obj1 = null //Ok |
[size=1em]1 [size=1em]2 [size=1em]3 [size=1em]4 [size=1em]5 [size=1em]6 | [size=1em][size=1em]private static Object myObj; [size=1em]public static void main(String args[]){ [size=1em] System.out.println("What is value of myObjc : " + myObj); [size=1em]} [size=1em]1 [size=1em]What is value of myObjc : null |
[size=1em]1 [size=1em]2 [size=1em]3 [size=1em]4 [size=1em]5 [size=1em]6 [size=1em]7 | [size=1em][size=1em]String str = null; // null can be assigned to String [size=1em]Integer itr = null; // you can assign null to Integer also [size=1em]Double dbl = null; // null can also be assigned to Double [size=1em] [size=1em]String myStr = (String) null; // null can be type cast to String [size=1em]Integer myItr = (Integer) null; // it can also be type casted to Integer [size=1em]Double myDbl = (Double) null; // yes it's possible, no error |
[size=1em]1 [size=1em]2 [size=1em]3 [size=1em]4 [size=1em]5 [size=1em]6 [size=1em]7 | [size=1em][size=1em]int i = null; // type mismatch : cannot convert from null to int [size=1em]short s = null; // type mismatch : cannot convert from null to short [size=1em]byte b = null: // type mismatch : cannot convert from null to byte [size=1em]double d = null; //type mismatch : cannot convert from null to double [size=1em] [size=1em]Integer itr = null; // this is ok [size=1em]int j = itr; // 这样转没问题,但是在运行时,会有空指针异常 |
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