Java – check whether the condition is’ null ‘

I have questions about checking null conditions For example:

if(some conditon)
value1= value;  //value1 is string type
else 
value1= "";

Similarly, the other four string values have similar conditions What I need is that I want to check whether all five string values are null in order to do some other specific parts I did

if(value1 == null)
{
}

However, the PGM control did not enter the loop, although value1 = "" Then I tried

if(value1 ==""){
}

It's no use

We can't check whether null and '' values are the same? Who can help me??

Solution

If you want to check whether the string is null, use

if (s == null)

If you want to check whether the string is empty, use

if (s.equals(""))

or

if (s.length() == 0)

or

if (s.isEmpty())

An empty string is an empty string It's not empty And = = must not be used to compare string contents== Test whether two variables refer to the same object instance If they contain the same characters, they will not