How do I remove the last " & " in a concatenation of Strings?

Question

I have a main class that is supposed to print the output to the console...

E.g. If the line contains A and B, I would need to print "Apple & Banana" on to the console, but with my current code, it prints as "Apple & Banana & "

I would do this in the main method by first instantiating an object of that class, i.e.

VeggiesAndFruits myVeg1 = new VeggiesAndFruits(AB);
VeggiesAndFruits myVeg2 = new VeggiesAndFruits(A);
System.out.println(myVeg1.getDescription());
System.out.println(myVeg2.getDescription());

Sample of code:

public class VeggiesAndFruits
{
String line;

public VeggiesAndFruits(String line)
{
this.line = line;
}

public String getDescription()
    {
        String description = "";

        if(line.contains("A"))
        {
            description += "Apple & ";
        }
        if(line.contains("B"))
        {
            description += "Banana & ";
        }
        if(line.contains("C"))
        {
            description += "Carrot & ";

        return description;
}
}

Answer 1

If using Java 8+, I suggest using a StringJoiner here. As the Javadoc says, StringJoiner is used to construct a sequence of characters separated by a delimiter. Like,

public String getDescription() {
    StringJoiner sj = new StringJoiner(" & ");

    if (line.contains("A")) {
        sj.add("Apple");
    }
    if (line.contains("B")) {
        sj.add("Banana");
    }
    if (line.contains("C")) {
        sj.add("Carrot");
    }
    return sj.toString();
}

And in earlier versions of Java (5+) you can use StringBuilder (and "glue" as kaya3 noted).

public String getDescription() {
    StringBuilder sb = new StringBuilder();
    String glue = "";
    if (line.contains("A")) {
        sb.append("Apple");
        glue = " & ";
    }
    if (line.contains("B")) {
        sb.append(glue);
        sb.append("Banana");
        glue = " & ";
    }
    if (line.contains("C")) {
        sb.append(glue);
        sb.append("Carrot");
    }
    return sb.toString();
}

Prior to Java 5, you could use a StringBuffer like

public String getDescription() {
    StringBuffer sb = new StringBuffer();
    String glue = "";
    if (line.contains("A")) {
        sb.append("Apple");
        glue = " & ";
    }
    if (line.contains("B")) {
        sb.append(glue);
        sb.append("Banana");
        glue = " & ";
    }
    if (line.contains("C")) {
        sb.append(glue);
        sb.append("Carrot");
    }
    return sb.toString();
}

Answer 2

In Java 8+, use StringJoiner:

public String getDescription() {
    StringJoiner description = new StringJoiner(" & ");
    if (line.contains("A"))
        description.add("Apple");
    if (line.contains("B"))
        description.add("Banana");
    if (line.contains("C"))
        description.add("Carrot");
    return description.toString();
}

In Java 5+, use StringBuilder and if statements:

public String getDescription() {
    StringBuilder description = new StringBuilder();
    if (line.contains("A")) {
        description.append("Apple");
    }
    if (line.contains("B")) {
        if (description.length() != 0)
            description.append(" & ");
        description.append("Banana");
    }
    if (line.contains("C")) {
        if (description.length() != 0)
            description.append(" & ");
        description.append("Carrot");
    }
    return description.toString();
}

Or, as pointed out by kaya3:

public String getDescription() {
    StringBuilder description = new StringBuilder();
    String sep = "";
    if (line.contains("A")) {
        description.append(sep).append("Apple");
        sep = " & ";
    }
    if (line.contains("B")) {
        description.append(sep).append("Banana");
        sep = " & ";
    }
    if (line.contains("C")) {
        description.append(sep).append("Carrot");
        sep = " & ";
    }
    return description.toString();
}

Or the way the question code is trying to do it:

public String getDescription() {
    StringBuilder description = new StringBuilder();
    if (line.contains("A"))
        description.append("Apple & ");
    if (line.contains("B"))
        description.append("Banana & ");
    if (line.contains("C"))
        description.append("Carrot & ");
    if (description.length() != 0)
        description.setLength(description.length() - 3); // remove final " & "
    return description.toString();
}

Test

System.out.println(new VeggiesAndFruits("").getDescription());
System.out.println(new VeggiesAndFruits("A").getDescription());
System.out.println(new VeggiesAndFruits("B").getDescription());
System.out.println(new VeggiesAndFruits("C").getDescription());
System.out.println(new VeggiesAndFruits("AB").getDescription());
System.out.println(new VeggiesAndFruits("AC").getDescription());
System.out.println(new VeggiesAndFruits("BC").getDescription());
System.out.println(new VeggiesAndFruits("CBA").getDescription());

Output (same for all 4 solutions above)

Apple
Banana
Carrot
Apple & Banana
Apple & Carrot
Banana & Carrot
Apple & Banana & Carrot

Answer 3

You can try using the int lastIndexOf(int ch) method on a string.

For example:

int index=description.lastIndexOf('&');

Then you can take a substring from the main string using this index to remove the last &.

String newDescription = description.substring(0, index);

Answer 4

Please have a look on a very important, valuable and old-but-gold class in Java called StringBuilder.

There are two points you could improve here:

1. To improve your memory handling in Java when you work with String objects: The concept of StringBuilder is quite straightforward and clear - to implement Builder Pattern and not to keep creating unnecessary new String objects after each concatenation of String values. This may not be obvious betterment when you have two or three Strings, but it's a huge advantage when you have many more Strings.. besides, it's way clearer code;

2. StringBuilder API provides methods out of the box on how to handle (concatenate, replace, substring and etc.) your String values. You can, for instance, use getChars(..), indexOf(..), lastIndexOf(..) and many more ready methods for your convenience.

Answer 5

Create a description builder class in your current class to cleanly handle generating your description. It will have one main method for adding content, and internally it will decide when to put an & sign and spaces if necessary using a putContent method that just creates the beginning of the description, and an appendContent method that adds more parts to the description.

class DescriptionBuilder {
    private String description = "";

    public DescriptionBuilder() {
    }

    //Use this method when adding content.
    public void addContent(String content) {
        if (description.isEmpty()) {
            putContent(content);
        } else {
            appendContent(content);
        }
    }

    //Get the built description
    @Override
    public String toString() {
        return description;
    }

    //Internally decided to create the start of the description
    private void putContent(String content) {
        description = content;
    }

    //Internally decided it's time to add more to the existing description
    private void appendContent(String content) {
        description += " & " + content;
    }
}

Then modify your getDescription method to use the description builder.

public String getDescription() {
        DescriptionBuilder descriptionBuilder = new DescriptionBuilder();

        if (line.contains("A")) {
            descriptionBuilder.addContent("Apple");
        }
        if (line.contains("B")) {
            descriptionBuilder.addContent("Banana");
        }
        if (line.contains("C")) {
            descriptionBuilder.addContent("Carrot");
        }
        return descriptionBuilder.toString();
    }

Answer 6

Without changing your sub class, In the main class you can remove last two character from out put (remove "&" and "final space" ), Also you missing double quotes " in the main method

VeggiesAndFruits myVeg1 = new VeggiesAndFruits(AB);

have to change as

VeggiesAndFruits myVeg1 = new VeggiesAndFruits("AB");

using String substring method you can remove last 2 charcter.

public static void main(String[] args) {
        VeggiesAndFruits myVeg1 = new VeggiesAndFruits("AB");
        String result ="";
        String str=myVeg1.getDescription();

        if ((str != null) && (str.length() > 0)) {
            result = str.substring(0, str.length() - 2);
        }
        System.out.println(result);         
    }