[英]Iterating over a Hashset of custom objects throws ClassCastException
[英]ClassCastException when iterating over HashSet
我有一个HashSet<String>
,里面装满了叫做shingles
的字符串(如果你把字符串“Fizzbuzz”打成碎片,你会得到“Fi”,“iz”,“zz”,“zb”,“bu” “,”“uz”,“zz”。不重要,但在这种背景下,这就是一块木瓦。
我试图通过以下方法返回HashSet内容的字符串:
public String getShinglesAsString() {
String shingles = "";
for (String shingle : this.shingles) {
shingles += shingle + " ";
}
return shingles;
}
for (String shingle : this.shingles)
抛出了ClassCastException。 特定消息是Exception in thread "main" java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.CharSequence
。
我也尝试过使用Iterator对象,我也遇到了同样的问题。 这是我的代码,用于从提供给构造函数的字符串生成带状疱疹:
// Will generate a new set of shingles based on sentence
public void generateShingles() {
shingles = new HashSet<>();
for (int i=0; i<getSentence().length()-1; i++) {
getShingles().add(getSentence().charAt(i) + getSentence().charAt(i+1));
}
}
编辑:这是最简单,完整,可验证的例子:
public class SentenceWithShingles {
private String sentence;
private Set<String> shingles;
// Constructor
public SentenceWithShingles(String sentence) {
this.sentence = sentence;
generateShingles();
}
// Will generate a new set of shingles based on sentence
public void generateShingles() {
shingles = new HashSet<>();
for (int i=0; i<getSentence().length()-1; i++) {
getShingles().add(getSentence().charAt(i) + getSentence().charAt(i+1));
}
}
public void setSentence(String sentence) {
this.sentence = sentence;
}
public Set getShingles() {
return shingles;
}
public String getShinglesAsString() {
String shingles = "";
for (String shingle : this.shingles) {
shingles += shingle + " ";
}
return shingles;
}
}
错误在这里:
getShingles().add(getSentence().charAt(i) + getSentence().charAt(i+1));
该行将两个字符加在一起。 没有连接它们。
getShingles().add(getSentence().charAt(i) + "" + getSentence().charAt(i+1));
将强制正确的语义。
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