String memory allocation and string pool concepts

Question

What is the difference between these two assignments, in terms of memory allocation and String pools.

String b = "sunil" + "khokhar";

and

String a = "sunil";
String b = a + "khokhar";

What do you think would happen? How do you think the compiler and the string pool would be different? Have you considered what difference using final might make? — Peter Lawrey
– Peter Lawrey, Commented Sep 24, 2014 at 6:46
what does it matter. what is your actual requirement for which you want to use the above approach. — vikeng21
– vikeng21, Commented Sep 24, 2014 at 6:54

TheLostMind · Accepted Answer · 2014-09-24 06:56:47Z

2

String b = "sunil" + "khokhar";

both "sunil" and "khokar" will be concatenated and the value of b will be resolved during compile-time. So, "sunilkhokhar will be present in the String constant pool. and

String a = "sunil";
String b = a + "khokhar";

"sunil" and "khokar" will be compile time constants (and be added to the String pool). But b = a+"khokhar" will be done using StringBuilder and will occur at runtime. So, b will be present in heap and not in the String constant pool.

answered Sep 24, 2014 at 6:56

TheLostMind

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Comments

Rohit Jadhav · Accepted Answer · 2014-09-24 07:05:53Z

0

String is a final class every time you user "+" and "=" new object will be created. For Variable assignments, if value already exists in pool then reference will be returned along with Object.

answered Sep 24, 2014 at 7:05

Rohit Jadhav

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4 Comments

TheLostMind Over a year ago

Not every time. No, only when you are using a reference which is not final during concatenation. So, a + "khokhar" will be resolved during compile time if a is final.

Sunil Khokhar Over a year ago

I think in case of String b="sunil"+"khokhar" only one object is created having value "sunilkhokhar" and one entry in string pool which refer this object.

Sunil Khokhar Over a year ago

and In case of String a = "sunil"; String b = a + "khokhar"; two object is created and 2 reference in. @TheLostMind correct me if a am wrong

TheLostMind Over a year ago

@SunilKhokhar - 3 String objects. "sunil" and "khokhar" will be in String constants pool and "sunilkhokhar" will be on heap. So, totally 3.

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