Difference between null and empty list in java

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Interview Questions. Company Questions. Artificial Intelligence. From the wikipedia article on empty string. String is not initialized for null. It will not throw null pointer. A string can be empty or have a null value. If a string is null , it isn't referring to anything in memory.

Try s. This is because if a string is empty, it still returns a length of 0. So if you enter nothing for the same, then it will still continue looping since it doesn't register the string as null. Whereas if you check for length, then it will exit out of it's loop.

This concept can be better understood from mathematics. Have you ever tried dividing a number not zero by 0 using a calculator e. You will get a result that looks like something this: undefined , not a number , null etc. This means that the operation is impossible, for some reasons let's leave those reasons to be discussed another day. You will get the output, 0. This means that the operation is possible and can be executed, but you the answer is just 0 because nothing is left after the division.

There is a valid output and that output is zero. In the first example, not only was the output invalid, the operation was not possible to execute. This is akin to null string in java. The second example is akin to empty string. It means there is a variable 'a' of type string which points to a object reference in string pool which has a value "". As variable a is holding a valid string object reference, all the methods of string can be applied here.

It means that there is a variable b of type string which points to an unknown reference. And any operation on unknown reference will result in an NullPointerException. For example: you have a variable named x. If you write in JS,. Actually this is like something but which is feel of nothing : On the other hand,. If you write y. With respect to real world both can be assumed same. Its just a syntax of a programming language that creates a difference between two as explained by others here.

This is a waste of processing power for every string comparisons. Here str1 is null meaning that you have defined it but not set any value for it yet, but you have defined str2 and set empty value for it so it has a value even that value is "";.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. You can memorize that easily because the method is directly called on the list the method belongs to the list.

So if there is no list, then there is no method. And Java will complain that there is no list to call this method on. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 9 years, 6 months ago. Active 2 years, 9 months ago. Viewed k times. Lii K'' K'' 4, 7 7 gold badges 27 27 silver badges 41 41 bronze badges. It can't. An NPE would be thrown before it could be invoked.

This "Will this throw a NullPointerException because test is null? You can easily test this question via a very simple test. Don't get me started about those stupid light bulbs. Boost this thread! Difference Between These 2 Declarations. Difference between String variable and String Object??? Help with Linked Lists.