问题描述
空字符串（ String s = null ）和空字符串（ String s =）？
What is the difference between a null string (String s = null) and an empty string (String s = "")?
这就是我所拥有的：
String s1 = ""; //print statement does not print any thing for s1 but s1.length()=0
String s2 = null;//print statement prints "null" for s2 but s2.length() gives exception
这是什么意思？
推荐答案
String s1 =; 表示空字符串已分配给 S1 。
在这种情况下， s1.length（）与。length（）相同，这将按预期产生 0 。
String s1 = ""; means that the empty String is assigned to s1.In this case, s1.length() is the same as "".length(), which will yield 0 as expected.
String s2 = null; 表示（ null ）或没有任何价值被分配给 s2 。所以这个， s2.length（）与 null.length（）相同，这将产生一个 NullPointerException 因为你无法用Java调用 null 变量（指针，排序）上的方法。
String s2 = null; means that (null) or "no value at all" is assigned to s2. So this one, s2.length() is the same as null.length(), which will yield a NullPointerException as you can't call methods on null variables (pointers, sort of) in Java.
另外，一个点，声明
String s1;
实际上具有与以下相同的效果：
Actually has the same effect as:
String s1 = null;
然而
String s1 = "";
如上所述，是另一回事。
Is, as said, a different thing.
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