Checking if two objects are equal even if they could be null

Question

Sometimes, I see this:

if (a.equals(b)) do(something);

However, if a is null, a NullPointerException is thrown. Assuming when a==null and b==null or if just a==b that I would want to do(something) . What's the simplest way to do this check without getting an exception?

Answer 1

另一种写作方式。

if (a == null ? b == null : a.equals(b))

Answer 2

if( a==b || (a!=null && a.equals(b)) )

(The a==b handles the case when both are null.)

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Also be aware of the Java 7 and above Object.equals method:

if(java.util.Object.equals(a, b))