which toString() method can be used performance wise?

Question

I am working on one project for performance enhancement. I had one doubt, while we are during a process, we tend to trace the current state of the DTO and entity used. So, for this we have included toString() method in all POJOs for the same. I have now implemented toString() in three different ways which are following :-

public String toString() {
    return "POJO :" + this.class.getName() + " RollNo :" + this.rollNo + " Name :" + this.name;
}

public String toString() {
    StringBuffer buff = new StringBuffer("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name);
    return buff.toString();
}

public String toString() {
        StringBuilder builder = new StringBuilder("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name);
        return builder .toString();
    }

can anyone please help me to find out which one is best and should be used for enhancing performance.

Answer 1

The one with the + is fine in this case. It's more readable, and it's just as performant compared to the StringBuilder/StringBuffer version, since it' doesn't happen inside a loop.

If you are building a String inside a loop, then more often than not you should use StringBuilder. Only use StringBuffer if you need its synchronized feature, which doesn't happen very often.

Simplistically speaking (not true always, but is a good rule of thumb), unless you're doing a += with a String, you don't really need a StringBuilder/StringBuffer.

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A String.format option

One option often not considered is to use String.format. It'll look something like this:

return String.format("POJO : %s RollNo %s : Name : %s",
   this.getClass().getName(),
   this.rollNo,
   this.name
);

I find that this is the most readable and maintainable version.

Is this faster? Maybe yes, maybe not. It usually doesn't matter for common use case scenarios for something like toString(). Strive for readability, only optimize if profiling says it's necessary.

API links

• java.util.Formatter syntax

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On Class Literals

I've corrected a syntax error in the original code from this.class (which doesn't compile) to this.getClass().

See also

• JLS 15.8.2 Class Literals

Related questions

• What is a class literal in Java ?