Java toString() method

Question

public String toString()
        {
        String str;
        str = "The test scores in descending order are \n";

        for(int i = 0; i < data.length; i++)
        {
            str = str + data[i] + " ";
        }
        str = str + "\nThe average is " + mean;
        return str;
        }

This code for java returns scores in descending order for my code. But what throws me off is the way the 'str' is being returned. How I understand this is the return value of 'str' is (str + "\nThe average is " + mean). Because this is my last updated value of 'str', it will update the 'str' to "The test scores in descending order are" First, Second the loop, then last "str + "\nThe average is " + mean". So in the end even though we updated str a few times the actually printed 'str' will only be "str + "\nThe average is " + mean". Please explain why the program actually ends up printing

The test scores in descending order are 70 80.......... (element values)

(And then returns the average mean value info)

Elliott Frisch · Accepted Answer · 2014-11-25 15:47:58Z

4

Because the command was

str = str + "\nThe average is " + mean;

Which means, append to everything already in str and store the results in str. If it was

str = "\nThe average is " + mean;

it would instead replace everything already in str.

answered Nov 25, 2014 at 15:47

Elliott Frisch

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6 Comments

Patrick White Over a year ago

It's easier for new programmers to understand once you grasp the idea that the right side of an assignment is calculated independently of the left side.

Wade Aston Over a year ago

Wow, that helps a lot! Thanks so much, once you point that out it's really obvious.

Wade Aston Over a year ago

Well there is actually something still unclear, why doesn't the for loop print the "The test scores in descending order are \n" and then the last element of the array? But instead prints all of the array elements. The command str = str + "\nThe average is " + mean; will append everything already in 'str' which seems like it would just be "The test scores...") and then the last element in the for loop?

Elliott Frisch Over a year ago

@WadeAston Because you only added it once. a+b is ab, ab+c is abc (not ababc).

Wade Aston Over a year ago

@ElliottFrisch I had to update the last comment it was vague.

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