Description
Parse the given text into a Number instance of the given target class, using the corresponding decode / valueOf method.
License
Apache License
Parameter
| Parameter | Description |
|---|
| text | the text to convert |
| targetClass | the target class to parse into |
Exception
| Parameter | Description |
|---|
| IllegalArgumentException | if the target class is not supported (i.e. not a standard Number subclass asincluded in the JDK) |
Return
the parsed number
Declaration
@SuppressWarnings("unchecked")
public static <T extends Number> T parseNumber(String text, Class<T> targetClass)
Method Source Code
//package com.java2s;
/*//ww w. j av a2 s. c om
* Copyright 2002-2015 the original author or authors. Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License. You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied. See the License for the specific language governing permissions and limitations under the
* License.
*/
import java.math.BigDecimal;
import java.math.BigInteger;
import java.text.DecimalFormat;
import java.text.NumberFormat;
import java.text.ParseException;
import java.util.Objects;
public class Main {
private static final BigInteger LONG_MIN = BigInteger.valueOf(Long.MIN_VALUE);
private static final BigInteger LONG_MAX = BigInteger.valueOf(Long.MAX_VALUE);
/**
* Parse the given {@code text} into a {@link Number} instance of the given target class, using the corresponding
* {@code decode} / {@code valueOf} method.
* <p>
* Trims the input {@code String} before attempting to parse the number.
* <p>
* Supports numbers in hex format (with leading "0x", "0X", or "#") as well.
*
* @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 Byte#decode
* @see Short#decode
* @see Integer#decode
* @see Long#decode
* @see #decodeBigInteger(String)
* @see Float#valueOf
* @see Double#valueOf
* @see BigDecimal#BigDecimal(String)
*/
@SuppressWarnings("unchecked")
public static <T extends Number> T parseNumber(String text, Class<T> targetClass) {
Objects.requireNonNull(text, "Text must not be null");
Objects.requireNonNull(targetClass, "Target class must not be null");
String trimmed = text.trim();
if (Byte.class == targetClass) {
return (T) (isHexNumber(trimmed) ? Byte.decode(trimmed) : Byte.valueOf(trimmed));
} else if (Short.class == targetClass) {
return (T) (isHexNumber(trimmed) ? Short.decode(trimmed) : Short.valueOf(trimmed));
} else if (Integer.class == targetClass) {
return (T) (isHexNumber(trimmed) ? Integer.decode(trimmed) : Integer.valueOf(trimmed));
} else if (Long.class == targetClass) {
return (T) (isHexNumber(trimmed) ? Long.decode(trimmed) : Long.valueOf(trimmed));
} else if (BigInteger.class == targetClass) {
return (T) (isHexNumber(trimmed) ? decodeBigInteger(trimmed) : new BigInteger(trimmed));
} else if (Float.class == targetClass) {
return (T) Float.valueOf(trimmed);
} else if (Double.class == targetClass) {
return (T) Double.valueOf(trimmed);
} else if (BigDecimal.class == targetClass || Number.class == targetClass) {
return (T) new BigDecimal(trimmed);
} else {
throw new IllegalArgumentException(
"Cannot convert String [" + text + "] to target class [" + targetClass.getName() + "]");
}
}
/**
* Parse the given {@code text} into a {@link Number} instance of the given target class, using the supplied
* {@link NumberFormat}.
* <p>
* Trims the input {@code String} before attempting to parse the number.
*
* @param text the text to convert
* @param targetClass the target class to parse into
* @param numberFormat the {@code NumberFormat} to use for parsing (if {@code null}, this method falls back to
* {@link #parseNumber(String, Class)})
* @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 NumberFormat#parse
* @see #convertNumberToTargetClass
* @see #parseNumber(String, Class)
*/
public static <T extends Number> T parseNumber(String text, Class<T> targetClass, NumberFormat numberFormat) {
if (numberFormat != null) {
Objects.requireNonNull(text, "Text must not be null");
Objects.requireNonNull(targetClass, "Target class must not be null");
DecimalFormat decimalFormat = null;
boolean resetBigDecimal = false;
if (numberFormat instanceof DecimalFormat) {
decimalFormat = (DecimalFormat) numberFormat;
if (BigDecimal.class == targetClass && !decimalFormat.isParseBigDecimal()) {
decimalFormat.setParseBigDecimal(true);
resetBigDecimal = true;
}
}
try {
Number number = numberFormat.parse(text.trim());
return convertNumberToTargetClass(number, targetClass);
} catch (ParseException ex) {
throw new IllegalArgumentException("Could not parse number: " + ex.getMessage());
} finally {
if (resetBigDecimal) {
decimalFormat.setParseBigDecimal(false);
}
}
} else {
return parseNumber(text, targetClass);
}
}
/**
* Determine whether the given {@code value} String indicates a hex number, i.e. needs to be passed into
* {@code Integer.decode} instead of {@code Integer.valueOf}, etc.
*/
private static boolean isHexNumber(String value) {
int index = (value.startsWith("-") ? 1 : 0);
return (value.startsWith("0x", index) || value.startsWith("0X", index) || value.startsWith("#", index));
}
/**
* Decode a {@link BigInteger} from the supplied {@link String} value.
* <p>
* 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);
}
/**
* 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 Byte
* @see Short
* @see Integer
* @see Long
* @see BigInteger
* @see Float
* @see Double
* @see BigDecimal
*/
@SuppressWarnings("unchecked")
public static <T extends Number> T convertNumberToTargetClass(Number number, Class<T> targetClass)
throws IllegalArgumentException {
Objects.requireNonNull(number, "Number must not be null");
Objects.requireNonNull(targetClass, "Target class must not be null");
if (targetClass.isInstance(number)) {
return (T) number;
} else if (Byte.class == targetClass) {
long value = number.longValue();
if (value < Byte.MIN_VALUE || value > Byte.MAX_VALUE) {
raiseOverflowException(number, targetClass);
}
return (T) Byte.valueOf(number.byteValue());
} else if (Short.class == targetClass) {
long value = number.longValue();
if (value < Short.MIN_VALUE || value > Short.MAX_VALUE) {
raiseOverflowException(number, targetClass);
}
return (T) Short.valueOf(number.shortValue());
} else if (Integer.class == targetClass) {
long value = number.longValue();
if (value < Integer.MIN_VALUE || value > Integer.MAX_VALUE) {
raiseOverflowException(number, targetClass);
}
return (T) Integer.valueOf(number.intValue());
} else if (Long.class == targetClass) {
BigInteger bigInt = null;
if (number instanceof BigInteger) {
bigInt = (BigInteger) number;
} else if (number instanceof BigDecimal) {
bigInt = ((BigDecimal) number).toBigInteger();
}
// Effectively analogous to JDK 8's BigInteger.longValueExact()
if (bigInt != null && (bigInt.compareTo(LONG_MIN) < 0 || bigInt.compareTo(LONG_MAX) > 0)) {
raiseOverflowException(number, targetClass);
}
return (T) Long.valueOf(number.longValue());
} else if (BigInteger.class == targetClass) {
if (number instanceof BigDecimal) {
// do not lose precision - use BigDecimal's own conversion
return (T) ((BigDecimal) number).toBigInteger();
} else {
// original value is not a Big* number - use standard long conversion
return (T) BigInteger.valueOf(number.longValue());
}
} else if (Float.class == targetClass) {
return (T) Float.valueOf(number.floatValue());
} else if (Double.class == targetClass) {
return (T) Double.valueOf(number.doubleValue());
} else if (BigDecimal.class == targetClass) {
// always use BigDecimal(String) here to avoid unpredictability of BigDecimal(double)
// (see BigDecimal javadoc for details)
return (T) new BigDecimal(number.toString());
} else {
throw new IllegalArgumentException(
"Could not convert number [" + number + "] of type [" + number.getClass().getName()
+ "] to unsupported target class [" + targetClass.getName() + "]");
}
}
/**
* Raise an <em>overflow</em> 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
* @throws IllegalArgumentException
*/
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");
}
}
Related
- parseNumber(String number)
- parseNumber(String number)
- parseNumber(String s)
- parseNumber(String text, Class targetClass)
- parseNumber(String text, Class targetClass, NumberFormat numberFormat)
- parseNumeric(String value)