//时间格式可以改成自己想要的格式，例yyyy-MM-dd HH:mm等等。
private final static String formatyyyyMMddHHMM = "yyyyMMddHHmm";String currTime = "201911051500";SimpleDateFormat yearFormat = new SimpleDateFormat(formatyyyyMMddHHMM);
Date dateTime = yearFormat.parse(currTime);
Calendar calendar = Calendar.getInstance();
calendar.setTime(dateTime);
//减30分钟
calendar.add(Calendar.MINUTE, -30);
String lastTime = yearFormat.format(calendar.getTime());
System.out.println(lastTime);
//输出结果为：201911051430//减一小时
calendar.add(Calendar.HOUR_OF_DAY, -1);
String lastTime = yearFormat.format(calendar.getTime());
System.out.println(lastTime);
//输出结果为：201911051400//减一天
calendar.add(Calendar.DAY_OF_MONTH, -1);
String lastTime = yearFormat.format(calendar.getTime());
System.out.println(lastTime);
//输出结果为：201911041500//减一个月
calendar.add(Calendar.MONTH, -1);
String lastTime = yearFormat.format(calendar.getTime());
System.out.println(lastTime);
//输出结果为：201910051500