String vs char[]

Question

I have some slides from IBM named : \"From Java Code to Java Heap: Understanding the Memory Usage of Your Application\", that says, when we use String instead of <

Answer 1

In the JVM, a character variable is stored in a single 16-bit memory allocation and changes to that Java variable overwrite that same memory location.This makes creating or updating character variables very fast and memory-cheap, but increases the JVM's overhead compared to the static allocation as used in Strings.

The JVM stores Java Strings in a variable size memory space (essentially, an array), which is exactly the same size (plus 1, for the string termination character) of the string when the String object is created or first assigned a value. Thus, an object with initial value "HELP!" would be allocated 96 bits of storage ( 6 characters, each 16-bits in size). This value is considered immutable, allowing the JVM to inline references to that variable, making static string assignments very fast, and very compact, plus very efficient from the JVM point of view.

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