Java整数转换成字符

最新推荐文章于 2022-11-28 21:08:49 发布

Frozen_Wang

最新推荐文章于 2022-11-28 21:08:49 发布

阅读量8.6k

点赞数

CC 4.0 BY-SA版权

分类专栏： JAVA 文章标签： Java实现int转换成String

本文链接：https://blog.youkuaiyun.com/Frozen_Wang/article/details/48490725

JAVA 专栏收录该内容

9 篇文章

订阅专栏

本文探讨了Java中将整数转换为字符串的三种常见方法：`String.valueOf(i)`，`Integer.toString(i)`和`"" + i`。并指出对于Double, Float, Long类型也有相似的转换方式。此外，文章提出可以通过查看Java源码自行实现此类转换。" 132945163,19673913,MATLAB GUI实现无线传输模型,"['MATLAB', 'GUI开发', '无线通信', '信号处理', '通信模型']

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Java中提供了三种整数转换成字符串的方式，大家都很熟悉：

1. String s = String.valueOf(i);
2. String s = Integer.toString(i);
3. String s = "" + i;
注：Double, Float, Long 转成字串的方法大同小异。

然而自己实现呢？

其实也很简单，我们只要参考Java的源代码即可实现。那么我们来分析一下Java中将整数转换成字符串的函数源码。

<pre name="code" class="java">    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', '4', '4', '4', '4',
        '5', '5', '5', '5', '5', '5', '5', '5', '5', '5',
        '6', '6', '6', '6', '6', '6', '6', '6', '6', '6',
        '7', '7', '7', '7', '7', '7', '7', '7', '7', '7',
        '8', '8', '8', '8', '8', '8', '8', '8', '8', '8',
        '9', '9', '9', '9', '9', '9', '9', '9', '9', '9',
        } ;

    final static char [] DigitOnes = {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        } ;

public static String toString(int i) {
        if (i == Integer.MIN_VALUE)
            return "-2147483648";

<span style="white-space:pre">	</span>//求整数的位数，当x为负数时，是以它的绝对值求的位数，因此需要给它加上一位负号位
        int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
        char[] buf = new char[size];//定义一个缓冲字符数组
        getChars(i, size, buf);//将整数分解为字符分别存入字符数组
        return new String(buf, true);//利用字符数组构造字符串
    }

    /**
     * Places characters representing the integer i into the
     * character array buf. The characters are placed into
     * the buffer backwards starting with the least significant
     * digit at the specified index (exclusive), and working
     * backwards from there.
     *
     * Will fail if i == Integer.MIN_VALUE
     */
    static void getChars(int i, int index, char[] buf) {
        int q, r;
        int charPos = index;
        char sign = 0;

        if (i < 0) {
            sign = '-';
            i = -i;
        }

        // Generate two digits per iteration
        while (i >= 65536) {
            q = i / 100;
        // really: r = i - (q * 100);
            r = i - ((q << 6) + (q << 5) + (q << 2));
            i = q;
            buf [--charPos] = DigitOnes[r];
            buf [--charPos] = DigitTens[r];
        }

        // Fall thru to fast mode for smaller numbers
        // assert(i <= 65536, i);
        for (;;) {
            q = (i * 52429) >>> (16+3);
            r = i - ((q << 3) + (q << 1));  // r = i-(q*10) ...
            buf [--charPos] = digits [r];
            i = q;
            if (i == 0) break;
        }
        if (sign != 0) {
            buf [--charPos] = sign;
        }
    }

    final static int [] sizeTable = { 9, 99, 999, 9999, 99999, 999999, 9999999,
                                      99999999, 999999999, Integer.MAX_VALUE };

    // Requires positive x 提供整数 X,返回x的位数
    static int stringSize(int x) {
        for (int i=0; ; i++)
            if (x <= sizeTable[i])
                return i+1;
    }