java计算上下午

上午为0，下午为1

GregorianCalendar ca = new GregorianCalendar();  
int ampm = ca.get(GregorianCalendar.AM_PM);

如果需要返回上下午

String amOrpm = "";

GregorianCalendar ca = new GregorianCalendar();  
int ampm = ca.get(GregorianCalendar.AM_PM);
if(ampm == 0){
amOrpm = "上午";
} else if(ampm == 1) {
amOrpm = "下午";
}