Java String declaration

Question

What is the difference between String str   new String  SOME   and String str  SOME  Does these declarations gives performance variation

User · Answer

There is a small difference between both.

Second declaration assignates the reference associated to the constant SOMEto the variable str

First declaration creates a new String having for value the value of the constant SOME and assignates its reference to the variable str.

In the first case, a second String has been created having the same value that SOME which implies more inititialization time. As a consequence, you should avoid it. Furthermore, at compile time, all constants SOMEare transformed into the same instance, which uses far less memory.

As a consequence, always prefer second syntax.

User · Answer

First one will create new String object in heap and str will refer it  In addition literal will also be placed in String pool  It means 2 objects will be created and 1 reference variable   Second option will create String literal in pool only and str will refer it  So only 1 Object will be created and 1 reference  This option will use the instance from String pool always rather than creating new one each time it is executed

User · Answer

String str   new String  SOME     always create a new object on the heap  String str  SOME     uses the String pool  Try this small example           String s1   new String  hello            String s2    hello           String s3    hello            System err println s1    s2           System err println s2    s3     To avoid creating unnecesary objects on the heap use the second form

User · Answer

String s1    Welcome      Does not create a new instance   String s2   new String  Welcome       Creates two objects and one reference variable

[java] Java String declaration

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