Convert Number To Target Class
import java.math.BigDecimal;
import java.math.BigInteger;
import java.text.NumberFormat;
import java.text.ParseException;
/**
* Miscellaneous utility methods for number conversion and parsing.
* Mainly for internal use within the framework; consider Jakarta's
* Commons Lang for a more comprehensive suite of string utilities.
*
* @author Juergen Hoeller
* @author Rob Harrop
* @since 1.1.2
*/
public abstract class NumberUtils {
/**
* Convert the given number into an instance of the given target class.
*
* @param number the number to convert
* @param targetClass the target class to convert to
* @return the converted number
* @throws IllegalArgumentException if the target class is not supported
* (i.e. not a standard Number subclass as included in the JDK)
* @see java.lang.Byte
* @see java.lang.Short
* @see java.lang.Integer
* @see java.lang.Long
* @see java.math.BigInteger
* @see java.lang.Float
* @see java.lang.Double
* @see java.math.BigDecimal
*/
public static Number convertNumberToTargetClass(Number number, Class targetClass)
throws IllegalArgumentException {
if (targetClass.isInstance(number)) {
return number;
} else if (targetClass.equals(Byte.class)) {
long value = number.longValue();
if (value < Byte.MIN_VALUE || value > Byte.MAX_VALUE) {
raiseOverflowException(number, targetClass);
}
return number.byteValue();
} else if (targetClass.equals(Short.class)) {
long value = number.longValue();
if (value < Short.MIN_VALUE || value > Short.MAX_VALUE) {
raiseOverflowException(number, targetClass);
}
return number.shortValue();
} else if (targetClass.equals(Integer.class)) {
long value = number.longValue();
if (value < Integer.MIN_VALUE || value > Integer.MAX_VALUE) {
raiseOverflowException(number, targetClass);
}
return number.intValue();
} else if (targetClass.equals(Long.class)) {
return number.longValue();
} else if (targetClass.equals(Float.class)) {
return number.floatValue();
} else if (targetClass.equals(Double.class)) {
return number.doubleValue();
} else if (targetClass.equals(BigInteger.class)) {
return BigInteger.valueOf(number.longValue());
} else if (targetClass.equals(BigDecimal.class)) {
// using BigDecimal(String) here, to avoid unpredictability of BigDecimal(double)
// (see BigDecimal javadoc for details)
return new BigDecimal(number.toString());
} else {
throw new IllegalArgumentException("Could not convert number [" + number + "] of type [" +
number.getClass().getName() + "] to unknown target class [" + targetClass.getName() + "]");
}
}
/**
* Raise an overflow exception for the given number and target class.
*
* @param number the number we tried to convert
* @param targetClass the target class we tried to convert to
*/
private static void raiseOverflowException(Number number, Class targetClass) {
throw new IllegalArgumentException("Could not convert number [" + number + "] of type [" +
number.getClass().getName() + "] to target class [" + targetClass.getName() + "]: overflow");
}
/**
* Parse the given text into a number instance of the given target class,
* using the corresponding default <code>decode</code> methods. Trims the
* input <code>String</code> before attempting to parse the number. Supports
* numbers in hex format (with leading 0x) and in octal format (with leading 0).
*
* @param text the text to convert
* @param targetClass the target class to parse into
* @return the parsed number
* @throws IllegalArgumentException if the target class is not supported
* (i.e. not a standard Number subclass as included in the JDK)
* @see java.lang.Byte#decode
* @see java.lang.Short#decode
* @see java.lang.Integer#decode
* @see java.lang.Long#decode
* @see #decodeBigInteger(String)
* @see java.lang.Float#valueOf
* @see java.lang.Double#valueOf
* @see java.math.BigDecimal#BigDecimal(String)
*/
public static Number parseNumber(String text, Class targetClass) {
String trimmed = text.trim();
if (targetClass.equals(Byte.class)) {
return Byte.decode(trimmed);
} else if (targetClass.equals(Short.class)) {
return Short.decode(trimmed);
} else if (targetClass.equals(Integer.class)) {
return Integer.decode(trimmed);
} else if (targetClass.equals(Long.class)) {
return Long.decode(trimmed);
} else if (targetClass.equals(BigInteger.class)) {
return decodeBigInteger(trimmed);
} else if (targetClass.equals(Float.class)) {
return Float.valueOf(trimmed);
} else if (targetClass.equals(Double.class)) {
return Double.valueOf(trimmed);
} else if (targetClass.equals(BigDecimal.class) || targetClass.equals(Number.class)) {
return new BigDecimal(trimmed);
} else {
throw new IllegalArgumentException(
"Cannot convert String [" + text + "] to target class [" + targetClass.getName() + "]");
}
}
/**
* Parse the given text into a number instance of the given target class,
* using the given NumberFormat. Trims the input <code>String</code>
* before attempting to parse the number.
*
* @param text the text to convert
* @param targetClass the target class to parse into
* @param numberFormat the NumberFormat to use for parsing (if <code>null</code>,
* this method falls back to <code>parseNumber(String, Class)</code>)
* @return the parsed number
* @throws IllegalArgumentException if the target class is not supported
* (i.e. not a standard Number subclass as included in the JDK)
* @see java.text.NumberFormat#parse
* @see #convertNumberToTargetClass
* @see #parseNumber(String,Class)
*/
public static Number parseNumber(String text, Class targetClass, NumberFormat numberFormat) {
if (numberFormat != null) {
try {
Number number = numberFormat.parse(text.trim());
return convertNumberToTargetClass(number, targetClass);
}
catch (ParseException ex) {
throw new IllegalArgumentException(ex.getMessage());
}
} else {
return parseNumber(text, targetClass);
}
}
/**
* Decode a {@link java.math.BigInteger} from a {@link String} value.
* Supports decimal, hex and octal notation.
*
* @see BigInteger#BigInteger(String,int)
*/
private static BigInteger decodeBigInteger(String value) {
int radix = 10;
int index = 0;
boolean negative = false;
// Handle minus sign, if present.
if (value.startsWith("-")) {
negative = true;
index++;
}
// Handle radix specifier, if present.
if (value.startsWith("0x", index) || value.startsWith("0X", index)) {
index += 2;
radix = 16;
} else if (value.startsWith("#", index)) {
index++;
radix = 16;
} else if (value.startsWith("0", index) && value.length() > 1 + index) {
index++;
radix = 8;
}
BigInteger result = new BigInteger(value.substring(index), radix);
return (negative ? result.negate() : result);
}
}
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