遍历 HashSet 时出现 ClassCastException

Question

我有一个 HashSet<String>，里面充满了名为 shingles 的字符串（如果你把字符串 "Fizzbuzz" 分解成带状疱疹，你会得到 "Fi"， "iz"、"zz"、"zb"、"bu"、"uz"、"zz"。不重要，但这就是瓦片在这种情况下的含义）。

我正在尝试通过以下方法return 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 ClassCastException。具体消息为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，但我遇到了同样的问题。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 minmal, complete, verifiable example:

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;
}

}

Answer 1

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。不连接它们。

getShingles().add(getSentence().charAt(i) + "" + getSentence().charAt(i+1));

将强制使用正确的语义。

遍历 HashSet 时出现 ClassCastException

ClassCastException when iterating over HashSet

java

set

hashset

classcastexception