在java中如何从字符串中获取子字符串直到字符c？

String str = "Hello, World!";
char c = ',';
int index = str.indexOf(c);
String subString = str.substring(0, index);
System.out.println(subString); // 输出：Hello

String str = "Hello, World!";
char c = ',';
String[] parts = str.split(String.valueOf(c), 2);
String subString = parts[0];
System.out.println(subString); // 输出：Hello

String str = "Hello, World!";
char c = ',';
Pattern pattern = Pattern.compile(String.valueOf(c));
Matcher matcher = pattern.matcher(str);
String subString = matcher.replaceFirst("");
System.out.println(subString); // 输出：Hello