Package java.lang

Class Integer

java.lang.Object
java.lang.Number
java.lang.Integer
All Implemented Interfaces:
Serializable, Comparable<Integer>
public final class Integer
extends Number
implements Comparable<Integer>
The wrapper for the primitive type int.

Implementation note: The "bit twiddling" methods in this class use techniques described in Henry S. Warren, Jr.'s Hacker's Delight, (Addison Wesley, 2002) and Sean Anderson's Bit Twiddling Hacks.

Since:
1.0
See Also:
Long, Serialized Form

  • Field Summary

    Fields
    Modifier and Type Field Description
    static int MAX_VALUE
    Constant for the maximum int value, 231-1.
    static int MIN_VALUE
    Constant for the minimum int value, -231.
    static int SIZE
    Constant for the number of bits needed to represent an int in two's complement form.
    static Class<Integer> TYPE
    The Class object that represents the primitive type int.

  • Constructor Summary

    Constructors
    Constructor Description
    Integer​(int value)
    Constructs a new Integer with the specified primitive integer value.
    Integer​(String string)
    Constructs a new Integer from the specified string.

  • Method Summary

    Modifier and Type Method Description
    static int bitCount​(int i)
    Counts the number of 1 bits in the specified integer; this is also referred to as population count.
    byte byteValue()
    Returns this object's value as a byte.
    static int compare​(int lhs, int rhs)
    Compares two int values.
    int compareTo​(Integer object)
    Compares this object to the specified integer object to determine their relative order.
    static Integer decode​(String string)
    Parses the specified string and returns a Integer instance if the string can be decoded into an integer value.
    double doubleValue()
    Returns this object's value as a double.
    boolean equals​(Object o)
    Compares this instance with the specified object and indicates if they are equal.
    float floatValue()
    Returns this object's value as a float.
    static Integer getInteger​(String string)
    Returns the Integer value of the system property identified by string.
    static Integer getInteger​(String string, int defaultValue)
    Returns the Integer value of the system property identified by string.
    static Integer getInteger​(String string, Integer defaultValue)
    Returns the Integer value of the system property identified by string.
    int hashCode()
    Returns an integer hash code for this object.
    static int highestOneBit​(int i)
    Determines the highest (leftmost) bit of the specified integer that is 1 and returns the bit mask value for that bit.
    int intValue()
    Gets the primitive value of this int.
    long longValue()
    Returns this object's value as a long.
    static int lowestOneBit​(int i)
    Determines the lowest (rightmost) bit of the specified integer that is 1 and returns the bit mask value for that bit.
    static int numberOfLeadingZeros​(int i)
    Determines the number of leading zeros in the specified integer prior to the highest one bit.
    static int numberOfTrailingZeros​(int i)
    Determines the number of trailing zeros in the specified integer after the lowest one bit.
    static int parseInt​(String string)
    Parses the specified string as a signed decimal integer value.
    static int parseInt​(String string, int radix)
    Parses the specified string as a signed integer value using the specified radix.
    static int reverse​(int i)
    Reverses the order of the bits of the specified integer.
    static int reverseBytes​(int i)
    Reverses the order of the bytes of the specified integer.
    static int rotateLeft​(int i, int distance)
    Rotates the bits of the specified integer to the left by the specified number of bits.
    static int rotateRight​(int i, int distance)
    Rotates the bits of the specified integer to the right by the specified number of bits.
    short shortValue()
    Returns this object's value as a short.
    static int signum​(int i)
    Returns the value of the signum function for the specified integer.
    static String toBinaryString​(int i)
    Converts the specified integer into its binary string representation.
    static String toHexString​(int i)
    Converts the specified integer into its hexadecimal string representation.
    static String toOctalString​(int i)
    Converts the specified integer into its octal string representation.
    String toString()
    Returns a string containing a concise, human-readable description of this object.
    static String toString​(int i)
    Converts the specified integer into its decimal string representation.
    static String toString​(int i, int radix)
    Converts the specified signed integer into a string representation based on the specified radix.
    static Integer valueOf​(int i)
    Returns a Integer instance for the specified integer value.
    static Integer valueOf​(String string)
    Parses the specified string as a signed decimal integer value.
    static Integer valueOf​(String string, int radix)
    Parses the specified string as a signed integer value using the specified radix.

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Field Details

    • MAX_VALUE

      public static final int MAX_VALUE
      Constant for the maximum int value, 231-1.
      See Also:
      Constant Field Values

    • MIN_VALUE

      public static final int MIN_VALUE
      Constant for the minimum int value, -231.
      See Also:
      Constant Field Values

    • SIZE

      public static final int SIZE
      Constant for the number of bits needed to represent an int in two's complement form.
      Since:
      1.5
      See Also:
      Constant Field Values

    • TYPE

      public static final Class<Integer> TYPE
      The Class object that represents the primitive type int.

  • Constructor Details

    • Integer

      public Integer​(int value)
      Constructs a new Integer with the specified primitive integer value.
      Parameters:
      value - the primitive integer value to store in the new instance.

    • Integer

      public Integer​(String string) throws NumberFormatException
      Constructs a new Integer from the specified string.
      Parameters:
      string - the string representation of an integer value.
      Throws:
      NumberFormatException - if string cannot be parsed as an integer value.
      See Also:
      parseInt(String)

  • Method Details

    • byteValue

      public byte byteValue()
      Description copied from class: Number
      Returns this object's value as a byte. Might involve rounding and/or truncating the value, so it fits into a byte.
      Overrides:
      byteValue in class Number
      Returns:
      the primitive byte value of this object.

    • compareTo

      public int compareTo​(Integer object)
      Compares this object to the specified integer object to determine their relative order.
      Specified by:
      compareTo in interface Comparable<Integer>
      Parameters:
      object - the integer object to compare this object to.
      Returns:
      a negative value if the value of this integer is less than the value of object; 0 if the value of this integer and the value of object are equal; a positive value if the value of this integer is greater than the value of object.
      Since:
      1.2
      See Also:
      Comparable

    • compare

      public static int compare​(int lhs, int rhs)
      Compares two int values.
      Returns:
      0 if lhs = rhs, less than 0 if lhs < rhs, and greater than 0 if lhs > rhs.
      Since:
      1.7

    • decode

      public static Integer decode​(String string) throws NumberFormatException
      Parses the specified string and returns a Integer instance if the string can be decoded into an integer value. The string may be an optional minus sign "-" followed by a hexadecimal ("0x..." or "#..."), octal ("0..."), or decimal ("...") representation of an integer.
      Parameters:
      string - a string representation of an integer value.
      Returns:
      an Integer containing the value represented by string.
      Throws:
      NumberFormatException - if string cannot be parsed as an integer value.

    • doubleValue

      public double doubleValue()
      Description copied from class: Number
      Returns this object's value as a double. Might involve rounding.
      Specified by:
      doubleValue in class Number
      Returns:
      the primitive double value of this object.

    • equals

      public boolean equals​(Object o)
      Compares this instance with the specified object and indicates if they are equal. In order to be equal, o must be an instance of Integer and have the same integer value as this object.
      Overrides:
      equals in class Object
      Parameters:
      o - the object to compare this integer with.
      Returns:
      true if the specified object is equal to this Integer; false otherwise.
      See Also:
      Object.hashCode()

    • floatValue

      public float floatValue()
      Description copied from class: Number
      Returns this object's value as a float. Might involve rounding.
      Specified by:
      floatValue in class Number
      Returns:
      the primitive float value of this object.

    • getInteger

      public static Integer getInteger​(String string)
      Returns the Integer value of the system property identified by string. Returns null if string is null or empty, if the property can not be found or if its value can not be parsed as an integer.
      Parameters:
      string - the name of the requested system property.
      Returns:
      the requested property's value as an Integer or null.

    • getInteger

      public static Integer getInteger​(String string, int defaultValue)
      Returns the Integer value of the system property identified by string. Returns the specified default value if string is null or empty, if the property can not be found or if its value can not be parsed as an integer.
      Parameters:
      string - the name of the requested system property.
      defaultValue - the default value that is returned if there is no integer system property with the requested name.
      Returns:
      the requested property's value as an Integer or the default value.

    • getInteger

      public static Integer getInteger​(String string, Integer defaultValue)
      Returns the Integer value of the system property identified by string. Returns the specified default value if string is null or empty, if the property can not be found or if its value can not be parsed as an integer.
      Parameters:
      string - the name of the requested system property.
      defaultValue - the default value that is returned if there is no integer system property with the requested name.
      Returns:
      the requested property's value as an Integer or the default value.

    • hashCode

      public int hashCode()
      Description copied from class: Object
      Returns an integer hash code for this object. By contract, any two objects for which Object.equals(java.lang.Object) returns true must return the same hash code value. This means that subclasses of Object usually override both methods or neither method.

      Note that hash values must not change over time unless information used in equals comparisons also changes.

      See Writing a correct hashCode method if you intend implementing your own hashCode method.

      Overrides:
      hashCode in class Object
      Returns:
      this object's hash code.
      See Also:
      Object.equals(java.lang.Object)

    • intValue

      public int intValue()
      Gets the primitive value of this int.
      Specified by:
      intValue in class Number
      Returns:
      this object's primitive value.

    • longValue

      public long longValue()
      Description copied from class: Number
      Returns this object's value as a long. Might involve rounding and/or truncating the value, so it fits into a long.
      Specified by:
      longValue in class Number
      Returns:
      the primitive long value of this object.

    • parseInt

      public static int parseInt​(String string) throws NumberFormatException
      Parses the specified string as a signed decimal integer value. The ASCII character - ('-') is recognized as the minus sign.
      Parameters:
      string - the string representation of an integer value.
      Returns:
      the primitive integer value represented by string.
      Throws:
      NumberFormatException - if string cannot be parsed as an integer value.

    • parseInt

      public static int parseInt​(String string, int radix) throws NumberFormatException
      Parses the specified string as a signed integer value using the specified radix. The ASCII character - ('-') is recognized as the minus sign.
      Parameters:
      string - the string representation of an integer value.
      radix - the radix to use when parsing.
      Returns:
      the primitive integer value represented by string using radix.
      Throws:
      NumberFormatException - if string cannot be parsed as an integer value, or radix < Character.MIN_RADIX || radix > Character.MAX_RADIX.

    • shortValue

      public short shortValue()
      Description copied from class: Number
      Returns this object's value as a short. Might involve rounding and/or truncating the value, so it fits into a short.
      Overrides:
      shortValue in class Number
      Returns:
      the primitive short value of this object.

    • toBinaryString

      public static String toBinaryString​(int i)
      Converts the specified integer into its binary string representation. The returned string is a concatenation of '0' and '1' characters.
      Parameters:
      i - the integer to convert.
      Returns:
      the binary string representation of i.

    • toHexString

      public static String toHexString​(int i)
      Converts the specified integer into its hexadecimal string representation. The returned string is a concatenation of characters from '0' to '9' and 'a' to 'f'.
      Parameters:
      i - the integer to convert.
      Returns:
      the hexadecimal string representation of i.

    • toOctalString

      public static String toOctalString​(int i)
      Converts the specified integer into its octal string representation. The returned string is a concatenation of characters from '0' to '7'.
      Parameters:
      i - the integer to convert.
      Returns:
      the octal string representation of i.

    • toString

      public String toString()
      Description copied from class: Object
      Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression: 
         getClass().getName() + '@' + Integer.toHexString(hashCode())

      See Writing a useful toString method if you intend implementing your own toString method.

      Overrides:
      toString in class Object
      Returns:
      a printable representation of this object.

    • toString

      public static String toString​(int i)
      Converts the specified integer into its decimal string representation. The returned string is a concatenation of a minus sign if the number is negative and characters from '0' to '9'.
      Parameters:
      i - the integer to convert.
      Returns:
      the decimal string representation of i.

    • toString

      public static String toString​(int i, int radix)
      Converts the specified signed integer into a string representation based on the specified radix. The returned string is a concatenation of a minus sign if the number is negative and characters from '0' to '9' and 'a' to 'z', depending on the radix. If radix is not in the interval defined by Character.MIN_RADIX and Character.MAX_RADIX then 10 is used as the base for the conversion.

      This method treats its argument as signed. If you want to convert an unsigned value to one of the common non-decimal bases, you may find toBinaryString(int), #toHexString, or toOctalString(int) more convenient.

      Parameters:
      i - the signed integer to convert.
      radix - the base to use for the conversion.
      Returns:
      the string representation of i.

    • valueOf

      public static Integer valueOf​(String string) throws NumberFormatException
      Parses the specified string as a signed decimal integer value.
      Parameters:
      string - the string representation of an integer value.
      Returns:
      an Integer instance containing the integer value represented by string.
      Throws:
      NumberFormatException - if string cannot be parsed as an integer value.
      See Also:
      parseInt(String)

    • valueOf

      public static Integer valueOf​(String string, int radix) throws NumberFormatException
      Parses the specified string as a signed integer value using the specified radix.
      Parameters:
      string - the string representation of an integer value.
      radix - the radix to use when parsing.
      Returns:
      an Integer instance containing the integer value represented by string using radix.
      Throws:
      NumberFormatException - if string cannot be parsed as an integer value, or radix < Character.MIN_RADIX || radix > Character.MAX_RADIX.
      See Also:
      parseInt(String, int)

    • highestOneBit

      public static int highestOneBit​(int i)
      Determines the highest (leftmost) bit of the specified integer that is 1 and returns the bit mask value for that bit. This is also referred to as the Most Significant 1 Bit. Returns zero if the specified integer is zero.
      Parameters:
      i - the integer to examine.
      Returns:
      the bit mask indicating the highest 1 bit in i.
      Since:
      1.5

    • lowestOneBit

      public static int lowestOneBit​(int i)
      Determines the lowest (rightmost) bit of the specified integer that is 1 and returns the bit mask value for that bit. This is also referred to as the Least Significant 1 Bit. Returns zero if the specified integer is zero.
      Parameters:
      i - the integer to examine.
      Returns:
      the bit mask indicating the lowest 1 bit in i.
      Since:
      1.5

    • numberOfLeadingZeros

      public static int numberOfLeadingZeros​(int i)
      Determines the number of leading zeros in the specified integer prior to the highest one bit.
      Parameters:
      i - the integer to examine.
      Returns:
      the number of leading zeros in i.
      Since:
      1.5

    • numberOfTrailingZeros

      public static int numberOfTrailingZeros​(int i)
      Determines the number of trailing zeros in the specified integer after the lowest one bit.
      Parameters:
      i - the integer to examine.
      Returns:
      the number of trailing zeros in i.
      Since:
      1.5

    • bitCount

      public static int bitCount​(int i)
      Counts the number of 1 bits in the specified integer; this is also referred to as population count.
      Parameters:
      i - the integer to examine.
      Returns:
      the number of 1 bits in i.
      Since:
      1.5

    • rotateLeft

      public static int rotateLeft​(int i, int distance)
      Rotates the bits of the specified integer to the left by the specified number of bits.
      Parameters:
      i - the integer value to rotate left.
      distance - the number of bits to rotate.
      Returns:
      the rotated value.
      Since:
      1.5

    • rotateRight

      public static int rotateRight​(int i, int distance)
      Rotates the bits of the specified integer to the right by the specified number of bits.
      Parameters:
      i - the integer value to rotate right.
      distance - the number of bits to rotate.
      Returns:
      the rotated value.
      Since:
      1.5

    • reverseBytes

      public static int reverseBytes​(int i)
      Reverses the order of the bytes of the specified integer.
      Parameters:
      i - the integer value for which to reverse the byte order.
      Returns:
      the reversed value.
      Since:
      1.5

    • reverse

      public static int reverse​(int i)
      Reverses the order of the bits of the specified integer.
      Parameters:
      i - the integer value for which to reverse the bit order.
      Returns:
      the reversed value.
      Since:
      1.5

    • signum

      public static int signum​(int i)
      Returns the value of the signum function for the specified integer.
      Parameters:
      i - the integer value to check.
      Returns:
      -1 if i is negative, 1 if i is positive, 0 if i is zero.
      Since:
      1.5

    • valueOf

      public static Integer valueOf​(int i)
      Returns a Integer instance for the specified integer value.

      If it is not necessary to get a new Integer instance, it is recommended to use this method instead of the constructor, since it maintains a cache of instances which may result in better performance.

      Parameters:
      i - the integer value to store in the instance.
      Returns:
      a Integer instance containing i.
      Since:
      1.5