public class RoundTool {
public static String round(double value, int dotNum) {
String strValue = String.valueOf(value);
int pos = strValue.indexOf(".");
int len = strValue.length();
int dotLen = len - pos - 1;
String endNum = "";
if (dotNum < dotLen) {
String c = strValue.substring(pos + dotNum + 1, pos + dotNum + 2);
int cNum = Integer.parseInt(c);
double tempValue = Double.parseDouble(strValue);
if (cNum >= 5) {
String tempDot = "";
for (int i = 0; i < dotNum - 1; i++) {
tempDot = tempDot + "0";
}
tempDot = "0." + tempDot + "1";
tempValue = tempValue + Double.parseDouble(tempDot);
strValue = String.valueOf(tempValue);
endNum = strValue.substring(0, strValue.indexOf(".") + dotNum + 1);
} else {
endNum = strValue.substring(0, strValue.indexOf(".") + dotNum + 1);
}
} else if (dotNum == dotLen) {
endNum = String.valueOf(value);
} else {
for (int i = 0; i <= dotNum - dotLen - 1; i++) {
strValue = strValue + "0";
}
endNum = strValue;
}
return endNum;
}
public static void main(String[] args) {
System.out.println("数值123.121保留两位小数:\t" + RoundTool.round(123.121, 2));
System.out.println("数值123.456789保留3位小数:\t" + RoundTool.round(123.456789, 3));
System.out.println("数值123.1231保留3位小数:\t" + RoundTool.round(123.1231, 3));
System.out.println("数值123.5保留3位小数:\t" + RoundTool.round(123.5, 3));
}
}
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