Java 库 String 类的 valueOf 方法大致可以分为三种：
- String.valueOf(Object)
- String.valueOf(char[])
- String.valueOf(基本数据类型)
String.valueOf(int i)源码：
public static String valueOf(int i) {
return Integer.toString(i);
}
Integer.toString(int i)源码：
public static String toString(int i) {
if (i == Integer.MIN_VALUE)
return "-2147483648";
int size = (i < 0) ? stringSize(-i) + 1 : stringSize(i);
char[] buf = new char[size];
getChars(i, size, buf);
return new String(buf, true);
}
Integer.getChars(int i, int index, char[] buf)的源码：
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;
}
}
其他方式实现MyString1 valueOf(int i)
public static MyString1 valueOf(int i) {
int n;
char[] temp;
int count;
if (i <= Character.MAX_VALUE)
return new MyString1(Character.toChars(i));
else {
n = i % Character.MAX_VALUE;
count = i / Character.MAX_VALUE;
temp = new char[count + 1];
temp[0] = (char) n;
for (int j = 1; j <= count; j++)
temp[j] = Character.MAX_VALUE;
return new MyString1(temp);
}
}