optimized the word pair save time

app/src/main/java/io/github/sspanak/tt9/db/sqlite/InsertOps.java

@@ -86,8 +86,16 @@ public class InsertOps {
 			return;
 		}
 
+		StringBuilder sql = new StringBuilder(
+			"INSERT INTO " + Tables.getWordPairs(langId) + " (word1, word2, sequence2) VALUES"
+		);
+
 		for (WordPair pair : pairs) {
-			db.insert(Tables.getWordPairs(langId), null, pair.toContentValues());
+			sql.append(pair.toSqlRow()).append(",");
 		}
+
+		sql.setLength(sql.length() - 1);
+
+		db.execSQL(sql.toString());
 	}
 }

app/src/main/java/io/github/sspanak/tt9/db/wordPairs/WordPair.java

@@ -1,7 +1,5 @@
 package io.github.sspanak.tt9.db.wordPairs;
 
-import android.content.ContentValues;
-
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
@@ -31,7 +29,7 @@ public class WordPair {
 			|| word1.isEmpty() || word2.isEmpty()
 			|| (word1.length() > SettingsStore.WORD_PAIR_MAX_WORD_LENGTH && word2.length() > SettingsStore.WORD_PAIR_MAX_WORD_LENGTH)
 			|| word1.equals(word2)
-			|| sequence2 == null || word2.length() != sequence2.length()
+			|| sequence2 == null || word2.length() != sequence2.length() || !(new Text(sequence2).isNumeric())
 			|| !(new Text(word1).isAlphabetic()) || !(new Text(word2).isAlphabetic());
 	}
 
@@ -42,15 +40,6 @@ public class WordPair {
 	}
 
 
-	public ContentValues toContentValues() {
-		ContentValues values = new ContentValues();
-		values.put("word1", word1);
-		values.put("word2", word2);
-		values.put("sequence2", sequence2);
-		return values;
-	}
-
-
 	@Override
 	public int hashCode() {
 		if (hash == null) {
@@ -67,6 +56,11 @@ public class WordPair {
 	}
 
 
+	public String toSqlRow() {
+		return "('" + word1 + "','" + word2 + "','" + sequence2 + "')";
+	}
+
+
 	@NonNull
 	@Override
 	public String toString() {

app/src/main/java/io/github/sspanak/tt9/util/Text.java

@@ -59,6 +59,20 @@ public class Text extends TextTools {
 		return true;
 	}
 
+	public boolean isNumeric() {
+		if (text == null) {
+			return false;
+		}
+
+		for (int i = 0, end = text.length(); i < end; i++) {
+			if (!Character.isDigit(text.charAt(i))) {
+				return false;
+			}
+		}
+
+		return true;
+	}
+
 	public boolean isEmpty() {
 		return text == null || text.isEmpty();
 	}