Java 获取历史时间和前一天特定时间的方法

public static String getHistoryTime(Integer his) {\n // 获取当前系统时间\n Calendar calendar = Calendar.getInstance();\n // 将当前时间向前调整his个小时\n calendar.add(Calendar.HOUR_OF_DAY, his);\n Date before = calendar.getTime();\n\n // 获取前3个小时整点时间\n calendar.setTime(before);\n calendar.set(Calendar.MINUTE, 0);\n calendar.set(Calendar.SECOND, 0);\n Date beforeRounded = calendar.getTime();\n\n // 格式化时间为字符串\n SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");\n String formattedTime = formatter.format(beforeRounded);\n return formattedTime;\n }\n获取前一天的 当前小时之前的时间内容：public static String getPreviousDayTime(Integer hour) {\n // 获取当前系统时间\n Calendar calendar = Calendar.getInstance();\n // 将当前时间向前调整一天\n calendar.add(Calendar.DAY_OF_MONTH, -1);\n Date previousDay = calendar.getTime();\n\n // 获取前一天的当前小时之前的时间\n calendar.setTime(previousDay);\n calendar.set(Calendar.HOUR_OF_DAY, hour);\n calendar.set(Calendar.MINUTE, 0);\n calendar.set(Calendar.SECOND, 0);\n Date previousDayRounded = calendar.getTime();\n\n // 格式化时间为字符串\n SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");\n String formattedTime = formatter.format(previousDayRounded);\n return formattedTime;\n }