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private String DateTransfer(String validEndTime){
try {
if(validEndTime.length() == 8){
validEndTime = validEndTime.substring(0, 4) + "." + validEndTime.substring(4, 6) + "." + validEndTime.substring(6, 8);
}
} catch (Exception e) {
}
return validEndTime;
}substring：
public String substring(int beginIndex, int endIndex) {
if (beginIndex < 0) {
throw new StringIndexOutOfBoundsException(beginIndex);
}
if (endIndex > value.length) {
throw new StringIndexOutOfBoundsException(endIndex);
}
int subLen = endIndex - beginIndex;
if (subLen < 0) {
throw new StringIndexOutOfBoundsException(subLen);
}
return ((beginIndex == 0) && (endIndex == value.length)) ? this
: new String(value, beginIndex, subLen);
}substring中，参数beginIndex 和endIndex
截取字符串比如前四位，要从0开始到4结束
因为subLen是endIndex-beginIndex，所以如果想要截取前四位 一定是4-0