Integer和Character · JAVA Base

###封装类中封装了，可能常用的方法。且有用的方法整理： #character | 函数名 |功能 | | --- | --- | | public static int digit(char ch, int radix) | Returns the numeric value of the character <code>ch</code> in the specified radix. ch转成各种进制表达的数字，超过范围则返回-1. | |public static int getNumericValue(char ch)|the numeric value of the character, as a nonnegative <code>int</code> value; -2 if the character has a numeric value that is not a nonnegative integer; -1 if the character has no numeric value.| |public static boolean isDigit(char ch)|| |public static boolean isLetter(char ch)|| |public static boolean isLetterOrDigit(char ch)|| |public static boolean isUpperCase(char ch)|| |public static boolean isLowerCase(char ch)|| ``` public class Main{ public static void main(String[] args) { System.out.println(Character.isLetter(' ')); System.out.println(Character.isLetter('a')); System.out.println(Character.isLetter('=')); System.out.println( Character.digit('f', 16)); System.out.println( Character.digit('f', 15)); System.out.println(Character.getNumericValue('a')); System.out.println(Character.getNumericValue('z')); } } 输出： false true false 15 -1 10 35 ``` #Integer | 函数名 |描述 | | --- | --- | | public static String toString(int i, int radix) | * Returns a string representation of the first argument in the radix specified by the second argument. 如果radix 在[2,35]中才有效，不然就默认成10进制| |public static String toOctalString(int i)|转8进制| |public static String toHexString(int i)|转16进制| |public static String toBinaryString(int i) |转2进制| |public static int numberOfLeadingZeros(int i)|Returns the number of zero bits preceding the highest-order ("leftmost") one-bit in the two's complement binary representation of the specified <tt>int</tt> value. Returns 32 if the specified value has no one-bits in its two's complement representation, in other words if it is equal to zero.| |public static int numberOfTrailingZeros(int i)|Returns the number of zero bits following the lowest-order ("rightmost") one-bit in the two's complement binary representation of the specified <tt>int</tt> value. Returns 32 if the specified value has no one-bits in its two's complement representation, in other words if it is equal to zero.| |public static int highestOneBit(int i)|@return an <tt>int</tt> value with a single one-bit, in the position of the highest-order one-bit in the specified value, or zero if the specified value is itself equal to zero.| |public static int lowestOneBit(int i) |@return an <tt>int</tt> value with a single one-bit, in the position of the lowest-order one-bit in the specified value, or zero if the specified value is itself equal to zero.| |public static int bitCount(int i)|@return the number of one-bits in the two's complement binary representation of the specified <tt>int</tt> value.| |public static int reverse(int i)|Returns the value obtained by reversing the order of the bits in the two's complement binary representation of the specified <tt>int</tt>value| |public static int parseInt(String s) throws NumberFormatException|Parses the string argument as a signed decimal integer.@exception NumberFormatException if the string does not contain a parsable integer.| |public static int parseInt(String s, int radix)throws NumberFormatException|Parses the string argument as a signed integer in the radix specified by the second argument *Examples: * <blockquote><pre> * parseInt("0", 10) returns 0 * parseInt("473", 10) returns 473 * parseInt("-0", 10) returns 0 * parseInt("-FF", 16) returns -255 * parseInt("1100110", 2) returns 102 * parseInt("2147483647", 10) returns 2147483647 * parseInt("-2147483648", 10) returns -2147483648 * parseInt("2147483648", 10) throws a NumberFormatException * parseInt("99", 8) throws a NumberFormatException * parseInt("Kona", 10) throws a NumberFormatException * parseInt("Kona", 27) returns 411787 * </pre></blockquote>| ``` public class Main{ public static void main(String[] args){ System.out.println(Integer.toString(8, 2)); System.out.println(Integer.toString(8,16)); System.out.println("numberOfLeadingZeros"); System.out.println(Integer.numberOfLeadingZeros(8)); System.out.println(Integer.numberOfLeadingZeros(0)); System.out.println(Integer.numberOfLeadingZeros(-1)); System.out.println(Integer.numberOfLeadingZeros(-2123)); System.out.println("highestOneBit"); System.out.println(Integer.highestOneBit(16)); System.out.println(Integer.highestOneBit(15)); System.out.println(Integer.highestOneBit(8)); System.out.println(Integer.highestOneBit(7)); System.out.println(Integer.highestOneBit(0)); System.out.println(Integer.highestOneBit(-1)); System.out.println(Integer.highestOneBit(-2123)); System.out.println("bitCount"); System.out.println(Integer.bitCount(16)); System.out.println(Integer.bitCount(3)); System.out.println(Integer.bitCount(-3)); System.out.println("reverse"); System.out.println(Integer.reverse(128)); System.out.println(Integer.reverse(16777216)); System.out.println(256*256); } } 输出： 1000 8 numberOfLeadingZeros 28 32 0 0 highestOneBit 16 8 8 4 0 -2147483648 -2147483648 bitCount 1 2 31 reverse 16777216 128 65536