为什么这段代码给我一个奇怪的输出
Why is this code giving me a strange output
下面的方法是为了制作一个数字的字符串版本，我知道已经有方法可以做到这一点，例如 String.valueOf()、Double.toString()，甚至只是 "" + someNumber.
private static String numToString(double i) {
String revNumber = "";
boolean isNeg = false;
if (i == 0) { //catch zero case
return "0";
}
if (i < 0) {
isNeg = true;
}
i = Math.abs(i);
while (i > 0) { //loop backwards through number, this loop
//finish, otherwise, i would not get any output in 'main()'
revNumber += "" + i % 10; //get the end
i /= 10; //slice end
}
String number = ""; //reversed
for (int k = revNumber.length() - 1; k >= 0; k--) {
number += revNumber.substring(k, k + 1);
}
revNumber = null; //let gc do its work
return isNeg ? "-" + number : number; //result expression to add "-"
//if needed.
}
虽然上面的方法应该只用于整数（32 位），我让它接受一个 double（64 位）参数并且我传递了一个 double 参数，没有小数，如果我也将 int 或小数等传递给方法，输出结果是相同的...
测试：
public static void main(String[] args) {
double test = -134; //Passing double arg
System.out.println(numToString(test)); //results
}
结果：（双倍最大内存结果？）：
-323-E5.1223-E33.1123-E43.1023-E43.1913-E43.1813-E43.1713-E43.1613-E43.1513-E43.1413-E43.1313-E43。 1213-E43.1113-E43.1013-E43.1903-E43.1803-E999999999999933.1703-E999999999999933.1603-E999999999999933.1503-E999999999999933.1403-E9899999999999933.1303-E999999999999933.1203-E999999999999933.1103-E8899999999999933.1003- E9899999999999933.1992-E999999999999933.1892-E999999999999933.1792-E999999999999933.1692-E999999999999933.1592-E999999999999933.1492-E999999999999933.1392-E999999999999933.1292-E999999999999933.1192-E999999999999933.1092-E999999999999933.1982-E999999999999933.1882-E1999999999999933. 1782-E999999999999933.1682-E999999999999933.1582-E999999999999933.1482-E999999999999933.1382-E999999999999933.1282-E1999999999999933.1182-E1999999999999933.1082-E2999999999999933.1972-E2999999999999933.1872-E3999999999999933.1772-E2999999999999933.1672-E1999999999999933.1572- E2999999999999933.1472-E999999999999933.1372-E999999999999933.1272-E199999999999933.1172-E2999999999999933.1072-E2999 999999999933.1962-E1999999999999933.1862-E999999999999933.1762-E999999999999933.1662-E999999999999933.1562-E999999999999933.1462-E999999999999933.1362-E999999999999933.1262-E999999999999933.1162-E999999999999933.1062-E999999999999933.1952-E999999999999933.1852-E999999999999933.1752- E999999999999933.1652-E999999999999933.1552-E999999999999933.1452-E999999999999933.1352-E999999999999933.1252-E999999999999933.1152-E999999999999933.1052-E9899999999999933.1942-E9899999999999933.1842-E999999999999933.1742-E999999999999933.1642-E999999999999933.1542-E999999999999933. 1442-E999999999999933.1342-E999999999999933.1242-E999999999999933.1142-E9899999999999933.1042-E999999999999933.1932-E8899999999999933.1832-E9899999999999933.1732-E8899999999999933.1632-E8899999999999933.1532-E8899999999999933.1432-E999999999999933.1332-E9899999999999933.1232- E8899999999999933.1132-E7899999999999933.1032-E8899999999999933.1922-E8899999999999933.1822-E7899999999999933.1722-E6899999999999933.1622-E5899999999999933.15 22-E5899999999999933.1422-E6899999999999933.1322-E6899999999999933.1222-E6899999999999933.1122-E7899999999999933.1022-E7899999999999933.1912-E7899999999999933.1812-E8899999999999933.1712-E8899999999999933.1612-E7899999999999933.1512-E7899999999999933.1412-E6899999999999933.1312- E6899999999999933.1212-E7899999999999933.1112-E7899999999999933.1012-E7899999999999933.1902-E7899999999999933.1802-E6899999999999933.1702-E7899999999999933.1602-E7899999999999933.1502-E8899999999999933.1402-E8899999999999933.1302-E8899999999999933.1202-E8899999999999933.1102-E7899999999999933. 1002-E7899999999999933.1991-E9899999999999933.1891-E9899999999999933.1791-E8899999999999933.1691-E7899999999999933.1591-E8899999999999933.1491-E8899999999999933.1391-E999999999999933.1291-E9899999999999933.1191-E9899999999999933.1091-E999999999999933.1981-E999999999999933.1881- E999999999999933.1781-E999999999999933.1681-E999999999999933.1581-E1999999999999933.1481-E999999999999933.1381-E999999999999933.1281-E199999999999993 3.1181-E2999999999999933.1081-E999999999999933.1971-E1999999999999933.1871-E999999999999933.1771-E2999999999999933.1671-E3999999999999933.1571-E3999999999999933.1471-E2999999999999933.1371-E2999999999999933.1271-E2999999999999933.1171-E999999999999933.1071-E999999999999933.1961- E999999999999933.1861-E999999999999933.1761-E999999999999933.1661-E999999999999933.1561-E999999999999933.1461-E8899999999999933.1361-E8899999999999933.1261-E8899999999999933.1161-E7899999999999933.1061-E7899999999999933.1951-E7899999999999933.1851-E7899999999999933.1751-E7899999999999933. 1651-E7899999999999933.1551-E6899999999999933.1451-E6899999999999933.1351-E6899999999999933.1251-E6899999999999933.1151-E6899999999999933.1051-E7899999999999933.1941-E6899999999999933.1841-E7899999999999933.1741-E7899999999999933.1641-E9899999999999933.1541-E999999999999933.1441- E999999999999933.1341-E999999999999933.1241-E999999999999933.1141-E999999999999933.1041-E999999999999933.1931-E9899999999999933.1831-E999999999999933.17 31-E999999999999933.1631-E8899999999999933.1531-E9899999999999933.1431-E9899999999999933.1331-E8899999999999933.1231-E8899999999999933.1131-E8899999999999933.1031-E7899999999999933.1921-E7899999999999933.1821-E7899999999999933.1721-E6899999999999933.1621-E7899999999999933.1521- E7899999999999933.1421-E8899999999999933.1321-E7899999999999933.1221-E7899999999999933.1121-E8899999999999933.1021-E8899999999999933.1911-E9899999999999933.1811-E999999999999933.1711-E999999999999933.1611-E999999999999933.1511-E999999999999933.1411-E1999999999999933.1311-E2999999999999933. 1211-E3999999999999933.1111-E2999999999999933.1011-E2999999999999933.1901-E3999999999999933.1801-E2999999999999933.1701-E2999999999999933.1601-E3999999999999933.1501-E2999999999999933.1401-E3999999999999933.1301-E3999999999999933.1201-E4999999999999933.1101-E5999999999999933.1001- E4999999999999933.199-E3999999999999933.189-E3999999999999933.179-E3999999999999933.169-E4999999999999933.159-E4999999999999933.149-E4999999999999933.1 39-E4999999999999933.129-E4999999999999933.119-E4999999999999933.109-E4999999999999933.198-E4999999999999933.188-E4999999999999933.178-E3999999999999933.168-E3999999999999933.158-E3999999999999933.148-E3999999999999933.138-E3999999999999933.128-E4999999999999933.118- E3999999999999933.108-E3999999999999933.197-E3999999999999933.187-E3999999999999933.177-E4999999999999933.167-E3999999999999933.157-E3999999999999933.147-E3999999999999933.137-E3999999999999933.127-E3999999999999933.117-E4999999999999933.107-E5999999999999933.196-E5999999999999933. 186-E5999999999999933.176-E4999999999999933.166-E4999999999999933.156-E4999999999999933.146-E4999999999999933.136-E3999999999999933.126-E3999999999999933.116-E3999999999999933.106-E3999999999999933.195-E2999999999999933.185-E1999999999999933.175-E2999999999999933.165- E2999999999999933.155-E2999999999999933.145-E2999999999999933.135-E3999999999999933.125-E4999999999999933.115-E4999999999999933.105-E2999999999999933.194-E1999999999999933.184-E299999 9999999933.174-E2999999999999933.164-E2999999999999933.154-E1999999999999933.144-E1999999999999933.134-E2999999999999933.124-E2999999999999933.114-E2999999999999933.104-E3999999999999933.193-E3999999999999933.183-E3999999999999933.173-E2999999999999933.163-E2999999999999933.153- E999999999999933.143-E2999999999999933.133-E2999999999999933.123-E2999999999999933.113-E3999999999999933.103-E3999999999999933.192-E3999999999999933.182-E3999999999999933.172-E3999999999999933.162-E4999999999999933.152-E4999999999999933.142-E5999999999999933.132-E6999999999999933. 122-E7999999999999933.112-E6999999999999933.102-E6999999999999933.191-E7999999999999933.181-E8999999999999933.171-E8999999999999933.161-E8999999999999933.151-E9999999999999933.141-E8999999999999933.131-E8999999999999933.121-E43.111-E43.101- E43.19-E1000000000000043.18-E1000000000000043.17-E43.16-E43.15-E43.14-E43.143100.04310.0431.043.14000000000000004.30.4
这不是编译器的问题。它正在发生，因为你正在做
i /= 10; //slice end
所以当你在第一个 运行 之后执行 13.4 时，它不会给你 1.34，它会给你类似 1.339999999999999999 的东西，也就是 1.34。
查看 Retain precision with double in Java 了解更多详情。
如果你只想反转数字你可以
private static String numToString(double i) {
String returnString = new StringBuilder(Double.toString(i)).reverse().toString();
return i>=0?returnString:"-"+returnString.substring(0,returnString.length()-1);
}
for (; i > 0; ) { //loop backwards through number
revNumber += "" + i % 10; //get the end
i /= 10; //slice end
}
这个循环永远不会结束，直到它在比它应该的时间晚得多的时间中断。 i % 10 不会切断双打的结尾。它适用于 int 但不适用于双精度。因此 134->13.4->1.34->.134-> 等等....所以你得到一个 argumentoutofrange 异常或类似的东西。否则，编译器只会继续为 double 可以处理的最大内存做这件事。
下面的方法是为了制作一个数字的字符串版本，我知道已经有方法可以做到这一点，例如 String.valueOf()、Double.toString()，甚至只是 "" + someNumber.
private static String numToString(double i) {
String revNumber = "";
boolean isNeg = false;
if (i == 0) { //catch zero case
return "0";
}
if (i < 0) {
isNeg = true;
}
i = Math.abs(i);
while (i > 0) { //loop backwards through number, this loop
//finish, otherwise, i would not get any output in 'main()'
revNumber += "" + i % 10; //get the end
i /= 10; //slice end
}
String number = ""; //reversed
for (int k = revNumber.length() - 1; k >= 0; k--) {
number += revNumber.substring(k, k + 1);
}
revNumber = null; //let gc do its work
return isNeg ? "-" + number : number; //result expression to add "-"
//if needed.
}
虽然上面的方法应该只用于整数（32 位），我让它接受一个 double（64 位）参数并且我传递了一个 double 参数，没有小数，如果我也将 int 或小数等传递给方法，输出结果是相同的...
测试：
public static void main(String[] args) {
double test = -134; //Passing double arg
System.out.println(numToString(test)); //results
}
结果：（双倍最大内存结果？）：
-323-E5.1223-E33.1123-E43.1023-E43.1913-E43.1813-E43.1713-E43.1613-E43.1513-E43.1413-E43.1313-E43。 1213-E43.1113-E43.1013-E43.1903-E43.1803-E999999999999933.1703-E999999999999933.1603-E999999999999933.1503-E999999999999933.1403-E9899999999999933.1303-E999999999999933.1203-E999999999999933.1103-E8899999999999933.1003- E9899999999999933.1992-E999999999999933.1892-E999999999999933.1792-E999999999999933.1692-E999999999999933.1592-E999999999999933.1492-E999999999999933.1392-E999999999999933.1292-E999999999999933.1192-E999999999999933.1092-E999999999999933.1982-E999999999999933.1882-E1999999999999933. 1782-E999999999999933.1682-E999999999999933.1582-E999999999999933.1482-E999999999999933.1382-E999999999999933.1282-E1999999999999933.1182-E1999999999999933.1082-E2999999999999933.1972-E2999999999999933.1872-E3999999999999933.1772-E2999999999999933.1672-E1999999999999933.1572- E2999999999999933.1472-E999999999999933.1372-E999999999999933.1272-E199999999999933.1172-E2999999999999933.1072-E2999 999999999933.1962-E1999999999999933.1862-E999999999999933.1762-E999999999999933.1662-E999999999999933.1562-E999999999999933.1462-E999999999999933.1362-E999999999999933.1262-E999999999999933.1162-E999999999999933.1062-E999999999999933.1952-E999999999999933.1852-E999999999999933.1752- E999999999999933.1652-E999999999999933.1552-E999999999999933.1452-E999999999999933.1352-E999999999999933.1252-E999999999999933.1152-E999999999999933.1052-E9899999999999933.1942-E9899999999999933.1842-E999999999999933.1742-E999999999999933.1642-E999999999999933.1542-E999999999999933. 1442-E999999999999933.1342-E999999999999933.1242-E999999999999933.1142-E9899999999999933.1042-E999999999999933.1932-E8899999999999933.1832-E9899999999999933.1732-E8899999999999933.1632-E8899999999999933.1532-E8899999999999933.1432-E999999999999933.1332-E9899999999999933.1232- E8899999999999933.1132-E7899999999999933.1032-E8899999999999933.1922-E8899999999999933.1822-E7899999999999933.1722-E6899999999999933.1622-E5899999999999933.15 22-E5899999999999933.1422-E6899999999999933.1322-E6899999999999933.1222-E6899999999999933.1122-E7899999999999933.1022-E7899999999999933.1912-E7899999999999933.1812-E8899999999999933.1712-E8899999999999933.1612-E7899999999999933.1512-E7899999999999933.1412-E6899999999999933.1312- E6899999999999933.1212-E7899999999999933.1112-E7899999999999933.1012-E7899999999999933.1902-E7899999999999933.1802-E6899999999999933.1702-E7899999999999933.1602-E7899999999999933.1502-E8899999999999933.1402-E8899999999999933.1302-E8899999999999933.1202-E8899999999999933.1102-E7899999999999933. 1002-E7899999999999933.1991-E9899999999999933.1891-E9899999999999933.1791-E8899999999999933.1691-E7899999999999933.1591-E8899999999999933.1491-E8899999999999933.1391-E999999999999933.1291-E9899999999999933.1191-E9899999999999933.1091-E999999999999933.1981-E999999999999933.1881- E999999999999933.1781-E999999999999933.1681-E999999999999933.1581-E1999999999999933.1481-E999999999999933.1381-E999999999999933.1281-E199999999999993 3.1181-E2999999999999933.1081-E999999999999933.1971-E1999999999999933.1871-E999999999999933.1771-E2999999999999933.1671-E3999999999999933.1571-E3999999999999933.1471-E2999999999999933.1371-E2999999999999933.1271-E2999999999999933.1171-E999999999999933.1071-E999999999999933.1961- E999999999999933.1861-E999999999999933.1761-E999999999999933.1661-E999999999999933.1561-E999999999999933.1461-E8899999999999933.1361-E8899999999999933.1261-E8899999999999933.1161-E7899999999999933.1061-E7899999999999933.1951-E7899999999999933.1851-E7899999999999933.1751-E7899999999999933. 1651-E7899999999999933.1551-E6899999999999933.1451-E6899999999999933.1351-E6899999999999933.1251-E6899999999999933.1151-E6899999999999933.1051-E7899999999999933.1941-E6899999999999933.1841-E7899999999999933.1741-E7899999999999933.1641-E9899999999999933.1541-E999999999999933.1441- E999999999999933.1341-E999999999999933.1241-E999999999999933.1141-E999999999999933.1041-E999999999999933.1931-E9899999999999933.1831-E999999999999933.17 31-E999999999999933.1631-E8899999999999933.1531-E9899999999999933.1431-E9899999999999933.1331-E8899999999999933.1231-E8899999999999933.1131-E8899999999999933.1031-E7899999999999933.1921-E7899999999999933.1821-E7899999999999933.1721-E6899999999999933.1621-E7899999999999933.1521- E7899999999999933.1421-E8899999999999933.1321-E7899999999999933.1221-E7899999999999933.1121-E8899999999999933.1021-E8899999999999933.1911-E9899999999999933.1811-E999999999999933.1711-E999999999999933.1611-E999999999999933.1511-E999999999999933.1411-E1999999999999933.1311-E2999999999999933. 1211-E3999999999999933.1111-E2999999999999933.1011-E2999999999999933.1901-E3999999999999933.1801-E2999999999999933.1701-E2999999999999933.1601-E3999999999999933.1501-E2999999999999933.1401-E3999999999999933.1301-E3999999999999933.1201-E4999999999999933.1101-E5999999999999933.1001- E4999999999999933.199-E3999999999999933.189-E3999999999999933.179-E3999999999999933.169-E4999999999999933.159-E4999999999999933.149-E4999999999999933.1 39-E4999999999999933.129-E4999999999999933.119-E4999999999999933.109-E4999999999999933.198-E4999999999999933.188-E4999999999999933.178-E3999999999999933.168-E3999999999999933.158-E3999999999999933.148-E3999999999999933.138-E3999999999999933.128-E4999999999999933.118- E3999999999999933.108-E3999999999999933.197-E3999999999999933.187-E3999999999999933.177-E4999999999999933.167-E3999999999999933.157-E3999999999999933.147-E3999999999999933.137-E3999999999999933.127-E3999999999999933.117-E4999999999999933.107-E5999999999999933.196-E5999999999999933. 186-E5999999999999933.176-E4999999999999933.166-E4999999999999933.156-E4999999999999933.146-E4999999999999933.136-E3999999999999933.126-E3999999999999933.116-E3999999999999933.106-E3999999999999933.195-E2999999999999933.185-E1999999999999933.175-E2999999999999933.165- E2999999999999933.155-E2999999999999933.145-E2999999999999933.135-E3999999999999933.125-E4999999999999933.115-E4999999999999933.105-E2999999999999933.194-E1999999999999933.184-E299999 9999999933.174-E2999999999999933.164-E2999999999999933.154-E1999999999999933.144-E1999999999999933.134-E2999999999999933.124-E2999999999999933.114-E2999999999999933.104-E3999999999999933.193-E3999999999999933.183-E3999999999999933.173-E2999999999999933.163-E2999999999999933.153- E999999999999933.143-E2999999999999933.133-E2999999999999933.123-E2999999999999933.113-E3999999999999933.103-E3999999999999933.192-E3999999999999933.182-E3999999999999933.172-E3999999999999933.162-E4999999999999933.152-E4999999999999933.142-E5999999999999933.132-E6999999999999933. 122-E7999999999999933.112-E6999999999999933.102-E6999999999999933.191-E7999999999999933.181-E8999999999999933.171-E8999999999999933.161-E8999999999999933.151-E9999999999999933.141-E8999999999999933.131-E8999999999999933.121-E43.111-E43.101- E43.19-E1000000000000043.18-E1000000000000043.17-E43.16-E43.15-E43.14-E43.143100.04310.0431.043.14000000000000004.30.4
这不是编译器的问题。它正在发生，因为你正在做
i /= 10; //slice end
所以当你在第一个 运行 之后执行 13.4 时，它不会给你 1.34，它会给你类似 1.339999999999999999 的东西，也就是 1.34。
查看 Retain precision with double in Java 了解更多详情。
如果你只想反转数字你可以
private static String numToString(double i) {
String returnString = new StringBuilder(Double.toString(i)).reverse().toString();
return i>=0?returnString:"-"+returnString.substring(0,returnString.length()-1);
}
for (; i > 0; ) { //loop backwards through number
revNumber += "" + i % 10; //get the end
i /= 10; //slice end
}
这个循环永远不会结束，直到它在比它应该的时间晚得多的时间中断。 i % 10 不会切断双打的结尾。它适用于 int 但不适用于双精度。因此 134->13.4->1.34->.134-> 等等....所以你得到一个 argumentoutofrange 异常或类似的东西。否则，编译器只会继续为 double 可以处理的最大内存做这件事。