How to return String.format with arrays

Question

When I print an instance of my class, the instance is referenced as "null" because I return "null", how can I format the toString class so it will return what I actually wrote in this function:

public String toString()
{
    System.out.print(this.coefficient);
    for(int i=0; i<26;i++)
    {
        if(degrees[i] == 1)
        {
            System.out.print(variables[i]);
        }
        if(degrees[i]>1)
        {
            System.out.print(variables[i] + "^" + degrees[i]);
        }
    }
    System.out.println('\n');
    return null;
}

For example, it has to return "m1 = 13a^2b^3" (it is a polynom) but instead is returns "13a^2b^3 m1 = null"

Well, don't print anything. Instead; concatenate the parts you want to return and return the result. Returning and printing are very different things. — JB Nizet, Apr 29 '17 at 19:05
Read [this](http://stackoverflow.com/questions/3615721/how-to-use-the-tostring-method-in-java) — Robin Topper, Apr 29 '17 at 19:07

score 1 · Accepted Answer · answered Apr 29 '17 at 19:10

Instead of directly printing each component of the String, concatenate them by using a StringBuilder:

public String toString()
{
    StringBuilder s = new StringBuilder();

    s.append(this.coefficient);
    for (int i = 0; i < 26; i++)
    {
        if (degrees[i] == 1)
        {
            s.append(variables[i]);
        }
        else if (degrees[i] > 1)
        {
            s.append(variables[i]).append('^').append(degrees[i]);
        }
    }

    return s.toString();
}

Vikrant · Answer 2 · 2017-04-29T19:19:24.937

-1

Use String Builder . Wherever you are using System.out.println

Instead of that

      StringBuilder temp=new StringBuilder();
      temp.append();// Add here the content what you are printing with Sysout 

       // at the end 
        return temp.toString();

edited Apr 29 '17 at 19:19

answered Apr 29 '17 at 19:10

Vikrant

178
4

How to return String.format with arrays

2 Answers2