Java 之 String 引用传递

方法一：

public static void DateTimeToString(String expr, String formatstr ,LocalDateTime now) {

String re = expr;
expr = "12345";
Field valueFieldOfString = null;
try {

valueFieldOfString = String.class.getDeclaredField("value");
valueFieldOfString.setAccessible(true);
valueFieldOfString.set(re,expr.toCharArray());

} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
}
}

方法二：使用 StringBuffuer ？ StringBuilder ？