Java 中给定一个字符串 与一个字符串集合，如何判定该字符串与字符串集合中每个字符串的相似度

cn.hutool.core.text.TextSimilarity

相似度的定义是什么

关键字：编辑距离

public class LevenshteinDistance {

public static int distance(String s1, String s2) {
int l1 = s1.length();
int l2 = s2.length();

// base cases
if (l1 == 0) return l2;
if (l2 == 0) return l1;

int[][] distance = new int[l1+1][l2+1];

for (int i = 0; i <= l1; i++) {
distance[i][0] = i;
}

for (int j = 0; j <= l2; j++) {
distance[0][j] = j;
}

for (int i = 1; i <= l1; i++) {
for (int j = 1; j <= l2; j++) {

int cost = (s1.charAt(i-1) == s2.charAt(j-1)) ? 0 : 1;

distance[i][j] = Math.min(
distance[i-1][j] + 1, // deletion
distance[i][j-1] + 1, // insertion
distance[i-1][j-1] + cost // substitution
);
}
}

return distance[l1][l2];
}

}

编辑距离，曾经给一个账号注册做优化，前人暴力比较，千万+的账号比完一个请求跑 3s 。

先定义相似度，问题要明确

这里还有其他关键字：
https://zh.wikipedia.org/wiki/Category:%E5%AD%97%E7%AC%A6%E4%B8%B2%E7%9B%B8%E4%BC%BC%E6%80%A7%E5%BA%A6%E9%87%8F

相似度算法。。

相似度的算法有好多，这个就要看你的数据类型了

https://github.com/tdebatty/java-string-similarity
推荐标准莱茵斯坦算法和余弦算法，字符串较大就用余弦，对准确率要求高就莱茵斯坦算法。
附上测试一个测试类自己修改下，用自己的实际数据多跑跑

public class SimilarityAlgorithmTest {

@Test
public void test() {
String str1 = "ares";
String str2 = "kele";

LevenshteinDistance levenshtein = LevenshteinDistance.getDefaultInstance();
System.out.println("Levenshtein distance: " + levenshtein.apply(str1, str2));
System.out.println("Levenshtein distance: " + levenshtein.apply(str2, str2));

LevenshteinDistance levenshteinWithThreshold = new LevenshteinDistance(3);
// Returns -1 since the actual distance, 4, is higher than the threshold
System.out.println("Levenshtein distance: " + levenshteinWithThreshold.apply(str1, str2));

LevenshteinDetailedDistance levenshteinDetailed = LevenshteinDetailedDistance.getDefaultInstance();
System.out.println("Levenshtein detailed distance: " + levenshteinDetailed.apply(str1, str2));
}

@Test
public void testLevenshteinDistance() {
int sLength = 13_162;
int strLength = 4_000;
String s = StringUtil.random(sLength);
String s1 = StringUtil.random(strLength) + s;
String s2 = StringUtil.random(strLength) + s;

int threshold = 4_096;
LevenshteinDistance levenshtein = new LevenshteinDistance(threshold);
long startTime = System.currentTimeMillis();
/*
threshold 为 32766 时花费 7022ms
threshold 为 16384 时花费 2164ms
threshold 为 8192 时花费 463ms
threshold 为 4096 时花费 146ms
threshold 为 2048 时花费 62ms
threshold 为 1024 时花费 41ms
threshold 为 512 时花费 29ms
*/
Integer result = levenshtein.apply(s1, s2);
System.out.println(System.currentTimeMillis() - startTime);
System.out.println("Levenshtein distance: " + result);

/*
这种是截取模式比较靠前的指定字符
threshold 为 4096 时花费 67ms
*/
levenshtein = LevenshteinDistance.getDefaultInstance();
startTime = System.currentTimeMillis();
result = levenshtein.apply(s1.substring(0, threshold), s2.substring(0, threshold));
System.out.println(System.currentTimeMillis() - startTime);
System.out.println("Levenshtein distance: " + result);
System.out.println();

result = levenshtein.apply(s1, s2);
System.out.println("Levenshtein: " + (1.0 - (double) result / (strLength + sLength)));
NormalizedLevenshtein normalizedLevenshtein = new NormalizedLevenshtein();
double similarity = normalizedLevenshtein.similarity(s1, s2);
System.out.println("NormalizedLevenshtein: " + similarity);
Jaccard jaccard = new Jaccard();
similarity = jaccard.similarity(s1, s2);
System.out.println("Jaccard: " + similarity);
Cosine cosine = new Cosine();
similarity = cosine.similarity(s1, s2);
System.out.println("Cosine: " + similarity);
QGram qGram = new QGram();
similarity = qGram.distance(s1, s2);
System.out.println("QGram: " + (1.0 - similarity / (strLength + sLength)));
}


@Test
public void testAlgorithmPerformance() {
String s1 = StringUtil.random(13_162);
String s2 = StringUtil.random(13_162);

LevenshteinDistance levenshtein = LevenshteinDistance.getDefaultInstance();
long startTime = System.currentTimeMillis();
levenshtein.apply(s1, s2);
System.out.println("LevenshteinDistance:" + (System.currentTimeMillis() - startTime));

NormalizedLevenshtein normalizedLevenshtein = new NormalizedLevenshtein();
startTime = System.currentTimeMillis();
normalizedLevenshtein.distance(s1, s2);
System.out.println("NormalizedLevenshtein: " + (System.currentTimeMillis() - startTime));

JaroWinkler jaroWinkler = new JaroWinkler();
startTime = System.currentTimeMillis();
jaroWinkler.distance(s1, s2);
System.out.println("JaroWinkler: " + (System.currentTimeMillis() - startTime));

LongestCommonSubsequence longestCommonSubsequence = new LongestCommonSubsequence();
startTime = System.currentTimeMillis();
longestCommonSubsequence.apply(s1, s2);
System.out.println("LongestCommonSubsequence: " + (System.currentTimeMillis() - startTime));

info.debatty.java.stringsimilarity.MetricLCS metricLCS = new info.debatty.java.stringsimilarity.MetricLCS();
startTime = System.currentTimeMillis();
metricLCS.distance(s1, s2);
System.out.println("MetricLCS: " + (System.currentTimeMillis() - startTime));

QGram qGram = new QGram();
startTime = System.currentTimeMillis();
qGram.distance(s1, s2);
System.out.println("QGram: " + (System.currentTimeMillis() - startTime));

Cosine cosine = new Cosine();
startTime = System.currentTimeMillis();
cosine.distance(s1, s2);
System.out.println("Cosine: " + (System.currentTimeMillis() - startTime));

Jaccard jaccard = new Jaccard();
startTime = System.currentTimeMillis();
jaccard.distance(s1, s2);
System.out.println("Jaccard: " + (System.currentTimeMillis() - startTime));
}

@Test
public void testCosine() {
String s1 = StringUtil.random(1_000_000);
String s2 = StringUtil.random(1_000_000);

Cosine cosine = new Cosine();
long startTime = System.currentTimeMillis();
cosine.distance(s1, s2);
System.out.println("Cosine: " + (System.currentTimeMillis() - startTime));
}

}

考虑集合效率的话，还可以用 SimHash