断断续续地，看完了Integer类，基本上了解了主要函数的原理之类的，下面是完整的源码和我的粗略翻译、注释以及一些吐槽。。有错请纠错QAQ。源码加注释之类的大概有1600多行，之后会挑几个重点难点的函数单独开博文讲，这里就当是个纪念~~学习的第一个Java类~
以下源码来自jdk的src.zip。
/*
* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. 版权说明
**/
package java.lang;
import java.lang.annotation.Native;
/**
* The {@code Integer} class wraps a value of the primitive type
* {@code int} in an object. An object of type {@code Integer}
* contains a single field whose type is {@code int}.
*
* <p>In addition, this class provides several methods for converting
* an {@code int} to a {@code String} and a {@code String} to an
* {@code int}, as well as other constants and methods useful when
* dealing with an {@code int}.
*
* <p>Implementation note: The implementations of the "bit twiddling"
* methods (such as {@link #highestOneBit(int) highestOneBit} and
* {@link #numberOfTrailingZeros(int) numberOfTrailingZeros}) are
* based on material from Henry S. Warren, Jr.'s <i>Hacker's
* Delight</i>, (Addison Wesley, 2002).
*
* @author Lee Boynton
* @author Arthur van Hoff
* @author Josh Bloch
* @author Joseph D. Darcy
* @since JDK1.0
*/
public final class Integer extends Number implements Comparable<Integer> {
/**
* A constant holding the minimum value an {@code int} can
* have, -2<sup>31</sup>.
*/
@Native public static final int MIN_VALUE = 0x80000000;
/**
* A constant holding the maximum value an {@code int} can
* have, 2<sup>31</sup>-1.
*/
@Native public static final int MAX_VALUE = 0x7fffffff;
/**
* The {@code Class} instance representing the primitive type
* {@code int}.
*
* @since JDK1.1
*/
@SuppressWarnings("unchecked")
public static final Class<Integer> TYPE = (Class<Integer>) Class.getPrimitiveClass("int");
/**
* All possible chars for representing a number as a String
* 所有可能被用来代表数字的字符
*/
final static char[] digits = {
'0' , '1' , '2' , '3' , '4' , '5' ,
'6' , '7' , '8' , '9' , 'a' , 'b' ,
'c' , 'd' , 'e' , 'f' , 'g' , 'h' ,
'i' , 'j' , 'k' , 'l' , 'm' , 'n' ,
'o' , 'p' , 'q' , 'r' , 's' , 't' ,
'u' , 'v' , 'w' , 'x' , 'y' , 'z'
};
/**
* Returns a string representation of the first argument in the
* radix specified by the second argument.
*
* <p>If the radix is smaller than {@code Character.MIN_RADIX}
* or larger than {@code Character.MAX_RADIX}, then the radix
* {@code 10} is used instead.
*
* <p>If the first argument is negative, the first element of the
* result is the ASCII minus character {@code '-'}
* ({@code '\u005Cu002D'}). If the first argument is not
* negative, no sign character appears in the result.
*
* <p>The remaining characters of the result represent the magnitude
* of the first argument. If the magnitude is zero, it is
* represented by a single zero character {@code '0'}
* ({@code '\u005Cu0030'}); otherwise, the first character of
* the representation of the magnitude will not be the zero
* character. The following ASCII characters are used as digits:
*
* <blockquote>
* {@code 0123456789abcdefghijklmnopqrstuvwxyz}
* </blockquote>
*
* These are {@code '\u005Cu0030'} through
* {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
* {@code '\u005Cu007A'}. If {@code radix} is
* <var>N</var>, then the first <var>N</var> of these characters
* are used as radix-<var>N</var> digits in the order shown. Thus,
* the digits for hexadecimal (radix 16) are
* {@code 0123456789abcdef}. If uppercase letters are
* desired, the {@link java.lang.String#toUpperCase()} method may
* be called on the result:
*
* <blockquote>
* {@code Integer.toString(n, 16).toUpperCase()}
* </blockquote>
*
* @param i an integer to be converted to a string.
* @param radix the radix to use in the string representation.
* @return a string representation of the argument in the specified radix.
* @see java.lang.Character#MAX_RADIX
* @see java.lang.Character#MIN_RADIX
*/
public static String toString(int i, int radix) {
if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX)
radix = 10;
//若进制（我理解radix为进制），超出规定范围，则默认进制为十进制
/* Use the faster version */
if (radix == 10) {
return toString(i);
}
char buf[] = new char[33];//因为int大小为32比特，33应该是保护不溢出
boolean negative = (i < 0);//传入的是否为负数，若为负数则为true，否则为false
int charPos = 32;
if (!negative) {
//如果i不为负数，应该是为了统一下面计算进制表示时都用负数，代码的复用么~
i = -i;
}
while (i <= -radix) { //栈，计算数字在不同进制下的表示方式
buf[charPos--] = digits[-(i % radix)]; //得到第i个字符，来表示数字
i = i / radix;
}
buf[charPos] = digits[-i];
if (negative) {
//如果i为负数，让第一个符号为‘-’，存在buf[32]中
buf[--charPos] = '-';
}
return new String(buf, charPos, (33 - charPos));//charPos开始的下标，33-charPos是有效数字的长度
}
/**
* Returns a string representation of the first argument as an
* unsigned integer value in the radix specified by the second
* argument.
*
* <p>If the radix is smaller than {@code Character.MIN_RADIX}
* or larger than {@code Character.MAX_RADIX}, then the radix
* {@code 10} is used instead.
*
* <p>Note that since the first argument is treated as an unsigned
* value, no leading sign character is printed.
*
* <p>If the magnitude is zero, it is represented by a single zero
* character {@code '0'} ({@code '\u005Cu0030'}); otherwise,
* the first character of the representation of the magnitude will
* not be the zero character.
*
* <p>The behavior of radixes and the characters used as digits
* are the same as {@link #toString(int, int) toString}.
*
* @param i an integer to be converted to an unsigned string.
* @param radix the radix to use in the string representation.
* @return an unsigned string representation of the argument in the specified radix.
* @see #toString(int, int)
* @since 1.8
*/
public static String toUnsignedString(int i, int radix) {
//返回一个无符号的数字字符串表示，复用了Long的同名方法
return Long.toUnsignedString(toUnsignedLong(i), radix);
//好像此处的radix意思为，1位数字用几位2进制数表示
}
/**
* Returns a string representation of the integer argument as an
* unsigned integer in base 16.
*
* <p>The unsigned integer value is the argument plus 2<sup>32</sup>
* if the argument is negative; otherwise, it is equal to the
* argument. This value is converted to a string of ASCII digits
* in hexadecimal (base 16) with no extra leading
* {@code 0}s.
* //如果传入的参数为负数，则将其加上2的32次方；否则不变。这个数值将被转换为十六进制，并且开头的0将被省去
*
* <p>The value of the argument can be recovered from the returned
* string {@code s} by calling {@link
* Integer#parseUnsignedInt(String, int)
* Integer.parseUnsignedInt(s, 16)}.
* //这个被转换的数可以通过调用Integer.parseUnsignedInt(s, 16)函数重新获得。
*
* <p>If the unsigned magnitude is zero, it is represented by a
* single zero character {@code '0'} ({@code '\u005Cu0030'});
* otherwise, the first character of the representation of the
* unsigned magnitude will not be the zero character. The
* following characters are used as hexadecimal digits:
* //除非这个数等于0，否则数的开头不会是0.接下来的数字将用十六进制的字符来表示，
* //如果希望字母为大写，可以调用String.toUpperCase()
*
* <blockquote>
* {@code 0123456789abcdef}
* </blockquote>
*
* These are the characters {@code '\u005Cu0030'} through
* {@code '\u005Cu0039'} and {@code '\u005Cu0061'} through
* {@code '\u005Cu0066'}. If uppercase letters are
* desired, the {@link java.lang.String#toUpperCase()} method may
* be called on the result:
*
* <blockquote>
* {@code Integer.toHexString(n).toUpperCase()}
* </blockquote>
*
* @param i an integer to be converted to a string.
* @return the string representation of the unsigned integer value
* represented by the argument in hexadecimal (base 16).
* @see #parseUnsignedInt(String, int)
* @see #toUnsignedString(int, int)
* @since JDK1.0.2
*/
public static String toHexString(int i) {
//将数值转换为十六进制后转String
return toUnsignedString0(i, 4);
}
/**
* Returns a string representation of the integer argument as an
* unsigned integer in base 8.
*
* <p>The unsigned integer value is the argument plus 2<sup>32</sup>
* if the argument is negative; otherwise, it is equal to the
* argument. This value is converted to a string of ASCII digits
* in octal (base 8) with no extra leading {@code 0}s.
*
* <p>The value of the argument can be recovered from the returned
* string {@code s} by calling {@link
* Integer#parseUnsignedInt(String, int)
* Integer.parseUnsignedInt(s, 8)}.
*
* <p>If the unsigned magnitude is zero, it is represented by a
* single zero character {@code '0'} ({@code '\u005Cu0030'});
* otherwise, the first character of the representation of the
* unsigned magnitude will not be the zero character. The
* following characters are used as octal digits:
*
* <blockquote>
* {@code 01234567}
* </blockquote>
*
* These are the characters {@code '\u005Cu0030'} through
* {@code '\u005Cu0037'}.
*
* @param i an integer to be converted to a string.
* @return the string representation of the unsigned integer value
* represented by the argument in octal (base 8).
* @see #parseUnsignedInt(String, int)
* @see #toUnsignedString(int, int)
* @since JDK1.0.2
*/
public static String toOctalString(int i) {
//将数值转换为八进制后转String
return toUnsignedString0(i, 3);
}
/**
* Returns a string representation of the integer argument as an
* unsigned integer in base 2.
*
* <p>The unsigned integer value is the argument plus 2<sup>32</sup>
* if the argument is negative; otherwise it is equal to the
* argument. This value is converted to a string of ASCII digits
* in binary (base 2) with no extra leading {@code 0}s.
*
* <p>The value of the argument can be recovered from the returned
* string {@code s} by calling {@link
* Integer#parseUnsignedInt(String, int)
* Integer.parseUnsignedInt(s, 2)}.
*
* <p>If the unsigned magnitude is zero, it is represented by a
* single zero character {@code '0'} ({@code '\u005Cu0030'});
* otherwise, the first character of the representation of the
* unsigned magnitude will not be the zero character. The
* characters {@code '0'} ({@code '\u005Cu0030'}) and {@code
* '1'} ({@code '\u005Cu0031'}) are used as binary digits.
*
* @param i an integer to be converted to a string.
* @return the string representation of the unsigned integer value
* represented by the argument in binary (base 2).
* @see #parseUnsignedInt(String, int)
* @see #toUnsignedString(int, int)
* @since JDK1.0.2
*/
public static String toBinaryString(int i) {
//将数值转换为二进制后转String
return toUnsignedString0(i, 1);
}
/**
* Convert the integer to an unsigned number.将int类型的数字转换成一个无符号数
*/
private static String toUnsignedString0(int val, int shift) {
// assert shift > 0 && shift <=5 : "Illegal shift value";
int mag = Integer.SIZE - Integer.numberOfLeadingZeros(val);
int chars = Math.max(((mag + (shift - 1)) / shift), 1);
char[] buf = new char[chars];
formatUnsignedInt(val, shift, buf, 0, chars);
// Use special constructor which takes over "buf".
return new String(buf, true);
}
/**
* Format a long (treated as unsigned) into a character buffer.
* @param val the unsigned int to format 无符号整数的格式
* @param shift the log2 of the base to format in (4 for hex, 3 for octal, 1 for binary)
* @param buf the character buffer to write to 字符数组缓冲区
* @param offset the offset in the destination buffer to start at 目标缓冲区的开始偏移量
* @param len the number of characters to write 写入的字符数
* @return the lowest character location used 低位字符？
*/
static int formatUnsignedInt(int val, int shift, char[] buf, int offset, int len) {
int charPos = len;
int radix = 1 << shift;//(10000 for hex ,1000 for octal ,10 for binary )
int mask = radix - 1; //掩码(1111 for hex, 111 for octal, 1 for binary)
do {
buf[offset + --charPos] = Integer.digits[val & mask];
val >>>= shift; // 无符号右移符，高位补0
} while (val != 0 && charPos > 0);
return charPos;
}
final static char [] DigitTens = {
'0', '0', '0', '0', '0', '0', '0', '0', '0', '0',
'1', '1', '1', '1', '1', '1', '1', '1', '1', '1',
'2', '2', '2', '2', '2', '2', '2', '2', '2', '2',
'3', '3', '3', '3', '3', '3', '3', '3', '3', '3',
'4', '4', '4', '4', '4', '4'
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