java - 将 String 转换为 int--java.lang.NumberFormatException.forInputString

Question

为什么这不起作用并抛出以下错误？

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

错误是:

 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)

此外，如果这不是将“A5”等字符串转换为整数的好方法，那么在 Java 中正确执行此操作的方法是什么？

我得到了一个类(我不应该修改它)，如下所示:

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

因此，当我实例化此类时，我需要传递给它的所有值(包括属性和标签都是字符串)，所以我不知道现在 Integer.ParseInt 失败了我应该做什么!

它暗示您可能想要从 DecTreeNode 类继承，但我不确定这是否相关!知道如何解决这个问题吗？

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

这是我收到的错误:

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

但是问题是我不允许修改 DecTreeNode 类以拥有新的构造函数。

这是不应修改的完整 DecTreeNode:

/**
 * 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);
        }
    }
}

这是 TrainingSet 类:

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

Answer 1

它告诉您“构造函数 DecTreeNode(String, String, int, boolean) 未定义”，因为您的类 DecTreeNode 没有定义具有这些数据类型的构造函数。您可以创建一个扩展 DecTreeNode 的类 DecTreeNodeImpl(如 DecTreeNode 类上的注释所示)并实现所有需要 String 类型参数的方法/构造函数。