Converting String to int--java.lang.NumberFormatException.forInputString

Question

Why would this not work and throw the following error?

System.out.println(Integer.parseInt("A5"));

Error is:

 at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.lang.Integer.parseInt(Integer.java:492)
        at java.lang.Integer.parseInt(Integer.java:527)
        at DecisionTreeImpl.createTree(DecisionTreeImpl.java:321)
        at DecisionTreeImpl.<init>(DecisionTreeImpl.java:59)

Also if this is not a good method for converting the strings like "A5" to integer, what's the way to do it correctly in Java?

I am given a class (and I am supposed not to modify it at all) which is like this:

public class DecTreeNode {
    Integer label; //for 
    Integer attribute;
    Integer parentAttributeValue; // if is the root, set to "-1"
    boolean terminal;
    List<DecTreeNode> children;

So when I am instantiating this class all the values which I need to pass to it (including attributes and labels are all string) so I have no idea what I should do now that Integer.ParseInt is failing me!

It is given as a hint that you might want to inherit from DecTreeNode class but I was not sure if that is related at all! Any idea how to tackle this problem?

root= new DecTreeNode((trainingSet.labels.get(getMajority(instances, trainingSet.labels.size())),trainingSet.attributes.get(biggestEntropy), -1, TRUE);

Here's the error I receive :

The constructor DecTreeNode(String, String, int, boolean) is undefined

However the problem is I am not allowed to modify the class DecTreeNode to have a new constructor.

Here's the complete DecTreeNode that is supposed not to be modified:

/**
 * Possible class for internal organization of a decision tree.
 * Included to show standardized output method, print().
 * 
 * Do not modify. If you use,
 * create child class DecTreeNodeImpl that inherits the methods.
 * 
 */
public class DecTreeNode {
    Integer label; //for 
    Integer attribute;
    Integer parentAttributeValue; // if is the root, set to "-1"
    boolean terminal;
    List<DecTreeNode> children;

    DecTreeNode(Integer _label, Integer _attribute, Integer _parentAttributeValue, boolean _terminal) {
        label = _label;
        attribute = _attribute;
        parentAttributeValue = _parentAttributeValue;
        terminal = _terminal;
        if (_terminal) {
            children = null;
        } else {
            children = new ArrayList<DecTreeNode>();
        }
    }

    /**
     * Add child to the node.
     * 
     * For printing to be consistent, children should be added
     * in order of the attribute values as specified in the
     * dataset.
     */
    public void addChild(DecTreeNode child) {
        if (children != null) {
            children.add(child);
        }
    }
}

Here's TrainingSet class:

public class DataSet {
    public List<String> labels = null;          // ordered list of class labels
    public List<String> attributes = null;      // ordered list of attributes
    public Map<String, List<String> > attributeValues = null; // map to ordered discrete values taken by attributes 
    public List<Instance> instances = null; // ordered list of instances
    private final String DELIMITER = ",";   // Used to split input strings

@Mona Jalal you cannot turn a non int to an int. Remove the A before the 5 lol :) — Alboz
– Alboz, Commented Oct 3, 2014 at 21:44
Your question seems like XY problem. Would you mind sharing with us more context like where does this string come from, why you want to convert it to integer (how are you going to use it)? — Pshemo
– Pshemo, Commented Oct 3, 2014 at 21:51

monica · Accepted Answer · 2014-10-03 22:32:30Z

1

It's telling you "The constructor DecTreeNode(String, String, int, boolean) is undefined" because your class DecTreeNode does not define a constructor with those data types. You can create a class DecTreeNodeImpl extending DecTreeNode(as the comments on the DecTreeNode class suggests) and implement all the methods/constructors that need parameters of type String.

answered Oct 3, 2014 at 22:32

monica

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Comments

maszter · Accepted Answer · 2014-10-03 21:50:15Z

0

If label is always one char, then solution is simple:

System.out.println(Integer.parseInt("A5".substring(1)));

answered Oct 3, 2014 at 21:50

maszter

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Comments

Alboz · Accepted Answer · 2014-10-03 22:05:59Z

0

Since we don't know how many letters there are (1 or more), I would personally go for something like this that removes all non-digits:

String labeledNumber="A5"

String str = labeledNumber.replaceAll("\\D+","");

System.out.println(Integer.parseInt(str));

This would work also with labels like: "abc12" "a-1232" etc.

edited Oct 3, 2014 at 22:05

answered Oct 3, 2014 at 22:00

Alboz

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5 Comments

Mona Jalal Over a year ago

This is not correct answer. I mentioned in various comments that input string can be anything. Not just hex.

Alboz Over a year ago

@Mona Jalal first try it and then judge. It's not hex! hex it's just a variable name. This will remove all the non numeric part of the string and keep the numbers!

Alboz Over a year ago

I changed the variable name :P

Alboz Over a year ago

@MonaJalal that's a big change, I'll give it a look :). Anyway this addresses what you asked at the beginning..

Mona Jalal Over a year ago

What you have written above, I believe doesn't differentiate between B5 and A5 per se! Right?

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