Integer represent primitive
* int values.
*
* Additionally, this class provides various helper functions and variables
* related to ints.
*
* @author Paul Fisher
* @author John Keiser
* @author Warren Levy
* @since JDK 1.0
*/
public final class Integer extends Number implements Comparable
{
// compatible with JDK 1.0.2+
private static final long serialVersionUID = 1360826667806852920L;
/**
* The minimum value an int can represent is -2147483648.
*/
public static final int MIN_VALUE = 0x80000000;
/**
* The maximum value an int can represent is 2147483647.
*/
public static final int MAX_VALUE = 0x7fffffff;
/**
* The primitive type int is represented by this
* Class object.
*/
public static final Class TYPE = VMClassLoader.getPrimitiveClass ("int");
/**
* The immutable value of this Integer.
*/
private final int value;
/**
* Create an Integer object representing the value of the
* int argument.
*
* @param value the value to use
*/
public Integer(int value)
{
this.value = value;
}
/**
* Create an Integer object representing the value of the
* argument after conversion to an int.
*
* @param s the string to convert.
*/
public Integer(String s) throws NumberFormatException
{
value = parseInt(s, 10);
}
/**
* Return a hashcode representing this Object.
*
* Integer's hash code is calculated by simply returning its
* value.
*
* @return this Object's hash code.
*/
public int hashCode()
{
return value;
}
/**
* If the Object is not null, is an
* instanceof Integer, and represents
* the same primitive int value return
* true. Otherwise false is returned.
*/
public boolean equals(Object obj)
{
return obj instanceof Integer && value == ((Integer)obj).value;
}
/**
* Get the specified system property as an Integer.
*
* The decode() method will be used to interpret the value of
* the property.
* @param nm the name of the system property
* @return the system property as an Integer, or
* null if the property is not found or cannot be
* decoded as an Integer.
* @see java.lang.System#getProperty(java.lang.String)
* @see #decode(int)
*/
public static Integer getInteger(String nm)
{
return getInteger(nm, null);
}
/**
* Get the specified system property as an Integer, or use a
* default int value if the property is not found or is not
* decodable.
*
* The decode() method will be used to interpret the value of
* the property.
*
* @param nm the name of the system property
* @param val the default value to use if the property is not found or not
* a number.
* @return the system property as an Integer, or the default
* value if the property is not found or cannot be decoded as an
* Integer.
* @see java.lang.System#getProperty(java.lang.String)
* @see #decode(int)
* @see #getInteger(java.lang.String,java.lang.Integer)
*/
public static Integer getInteger(String nm, int val)
{
Integer result = getInteger(nm, null);
return (result == null) ? new Integer(val) : result;
}
/**
* Get the specified system property as an Integer, or use a
* default Integer value if the property is not found or is
* not decodable.
*
* The decode() method will be used to interpret the value of
* the property.
*
* @param nm the name of the system property
* @param val the default value to use if the property is not found or not
* a number.
* @return the system property as an Integer, or the default
* value if the property is not found or cannot be decoded as an
* Integer.
* @see java.lang.System#getProperty(java.lang.String)
* @see #decode(int)
* @see #getInteger(java.lang.String,int)
*/
public static Integer getInteger(String nm, Integer def)
{
String val = System.getProperty(nm);
if (val == null) return def;
try
{
return decode(nm);
}
catch (NumberFormatException e)
{
return def;
}
}
private static String toUnsignedString(int num, int exp)
{
// Use an array large enough for a binary number.
int radix = 1 << exp;
int mask = radix - 1;
char[] buffer = new char[32];
int i = 32;
do
{
buffer[--i] = Character.forDigit(num & mask, radix);
num = num >>> exp;
}
while (num != 0);
return String.valueOf(buffer, i, 32-i);
}
/**
* Converts the int to a String assuming it is
* unsigned in base 16.
* @param i the int to convert to String
* @return the String representation of the argument.
*/
public static String toHexString(int i)
{
return toUnsignedString(i, 4);
}
/**
* Converts the int to a String assuming it is
* unsigned in base 8.
* @param i the int to convert to String
* @return the String representation of the argument.
*/
public static String toOctalString(int i)
{
return toUnsignedString(i, 3);
}
/**
* Converts the int to a String assuming it is
* unsigned in base 2.
* @param i the int to convert to String
* @return the String representation of the argument.
*/
public static String toBinaryString(int i)
{
return toUnsignedString(i, 1);
}
/**
* Converts the int to a String and assumes
* a radix of 10.
* @param i the int to convert to String
* @return the String representation of the argument.
*/
public static String toString(int i)
{
// This is tricky: in libgcj, String.valueOf(int) is a fast native
// implementation. In Classpath it just calls back to
// Integer.toString(int,int).
return String.valueOf (i);
}
/**
* Converts the Integer value to a String and
* assumes a radix of 10.
* @return the String representation of this Integer.
*/
public String toString()
{
return toString (value);
}
/**
* Converts the int to a String using
* the specified radix (base).
* @param i the int to convert to String.
* @param radix the radix (base) to use in the conversion.
* @return the String representation of the argument.
*/
public static String toString(int num, int radix)
{
if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
radix = 10;
// For negative numbers, print out the absolute value w/ a leading '-'.
// Use an array large enough for a binary number.
char[] buffer = new char[33];
int i = 33;
boolean isNeg;
if (num < 0)
{
isNeg = true;
num = -(num);
// When the value is MIN_VALUE, it overflows when made positive
if (num < 0)
{
buffer[--i] = Character.forDigit(-(num + radix) % radix, radix);
num = -(num / radix);
}
}
else
isNeg = false;
do
{
buffer[--i] = Character.forDigit(num % radix, radix);
num /= radix;
}
while (num > 0);
if (isNeg)
buffer[--i] = '-';
return String.valueOf(buffer, i, 33-i);
}
/**
* Creates a new Integer object using the String,
* assuming a radix of 10.
* @param s the String to convert.
* @return the new Integer.
* @see #Integer(java.lang.String)
* @see #parseInt(java.lang.String)
* @exception NumberFormatException thrown if the String
* cannot be parsed as an int.
*/
public static Integer valueOf(String s) throws NumberFormatException
{
return new Integer(parseInt(s));
}
/**
* Creates a new Integer object using the String
* and specified radix (base).
* @param s the String to convert.
* @param radix the radix (base) to convert with.
* @return the new Integer.
* @see #parseInt(java.lang.String,int)
* @exception NumberFormatException thrown if the String
* cannot be parsed as an int.
*/
public static Integer valueOf(String s, int radix)
throws NumberFormatException
{
return new Integer(parseInt(s, radix));
}
/**
* Converts the specified String into an int.
* This function assumes a radix of 10.
*
* @param s the String to convert
* @return the int value of the String
* argument.
* @exception NumberFormatException thrown if the String
* cannot be parsed as an int.
*/
public static int parseInt(String s) throws NumberFormatException
{
return parseInt(s, 10);
}
/**
* Converts the specified String into an int
* using the specified radix (base).
*
* @param s the String to convert
* @param radix the radix (base) to use in the conversion
* @return the String argument converted to int.
* @exception NumberFormatException thrown if the String
* cannot be parsed as a int.
*/
public static int parseInt(String str, int radix)
throws NumberFormatException
{
final int len;
if ((len = str.length()) == 0 ||
radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
throw new NumberFormatException();
boolean isNeg = false;
int index = 0;
if (str.charAt(index) == '-')
if (len > 1)
{
isNeg = true;
index++;
}
else
throw new NumberFormatException();
return parseInt(str, index, len, isNeg, radix);
}
private static int parseInt(String str, int index, int len, boolean isNeg,
int radix)
throws NumberFormatException
{
int val = 0;
int digval;
int max = MAX_VALUE / radix;
// We can't directly write `max = (MAX_VALUE + 1) / radix'.
// So instead we fake it.
if (isNeg && MAX_VALUE % radix == radix - 1)
++max;
for ( ; index < len; index++)
{
if (val < 0 || val > max)
throw new NumberFormatException();
if ((digval = Character.digit(str.charAt(index), radix)) < 0)
throw new NumberFormatException();
// Throw an exception for overflow if result is negative.
// However, we special-case the most negative value.
val = val * radix + digval;
if (val < 0 && (! isNeg || val != MIN_VALUE))
throw new NumberFormatException();
}
return isNeg ? -(val) : val;
}
/**
* Convert the specified String into an Integer.
* The String may represent decimal, hexadecimal, or
* octal numbers.
*
* The String argument is interpreted based on the leading
* characters. Depending on what the String begins with, the base will be
* interpreted differently:
*
* | Leading Characters | Base |
|---|---|
| # | 16 |
| 0x | 16 |
| 0X | 16 |
| 0 | 8 |
| Anything Else | 10 |
String to interpret.
* @return the value of the String as an Integer.
* @exception NumberFormatException thrown if the String
* cannot be parsed as an int.
*/
public static Integer decode(String str) throws NumberFormatException
{
boolean isNeg = false;
int index = 0;
int radix = 10;
final int len;
if (str == null || (len = str.length()) == 0)
throw new NumberFormatException("string null or empty");
// Negative numbers are always radix 10.
if (str.charAt(index) == '-')
{
radix = 10;
index++;
isNeg = true;
}
else if (str.charAt(index) == '#')
{
radix = 16;
index++;
}
else if (str.charAt(index) == '0')
{
// Check if str is just "0"
if (len == 1)
return new Integer(0);
index++;
if (str.charAt(index) == 'x' || str.charAt(index) == 'X')
{
radix = 16;
index++;
}
else
radix = 8;
}
if (index >= len)
throw new NumberFormatException("empty value");
return new Integer(parseInt(str, index, len, isNeg, radix));
}
/** Return the value of this Integer as a byte.
** @return the value of this Integer as a byte.
**/
public byte byteValue()
{
return (byte) value;
}
/** Return the value of this Integer as a short.
** @return the value of this Integer as a short.
**/
public short shortValue()
{
return (short) value;
}
/** Return the value of this Integer as an int.
** @return the value of this Integer as an int.
**/
public int intValue()
{
return value;
}
/** Return the value of this Integer as a long.
** @return the value of this Integer as a long.
**/
public long longValue()
{
return value;
}
/** Return the value of this Integer as a float.
** @return the value of this Integer as a float.
**/
public float floatValue()
{
return value;
}
/** Return the value of this Integer as a double.
** @return the value of this Integer as a double.
**/
public double doubleValue()
{
return value;
}
/**
* Compare two Integers numerically by comparing their
* int values.
* @return a positive value if this Integer is greater
* in value than the argument Integer; a negative value
* if this Integer is smaller in value than the argument
* Integer; and 0, zero, if this
* Integer is equal in value to the argument
* Integer.
*
* @since 1.2
*/
public int compareTo(Integer i)
{
if (this.value == i.value)
return 0;
// Returns just -1 or 1 on inequality; doing math might overflow.
if (this.value > i.value)
return 1;
return -1;
}
/**
* Behaves like compareTo(java.lang.Integer) unless the Object
* is not a Integer. Then it throws a
* ClassCastException.
* @exception ClassCastException if the argument is not a
* Integer.
*
* @since 1.2
*/
public int compareTo(Object o)
{
return compareTo((Integer)o);
}
}