java 怎么实现任意生成一个10位数？

/**
* 生成随机数字
* @param length
* @return
*/
public static final String randomNumber(int length) {
char[] numbersAndLetters = null;
java.util.Random randGen = null;
if (length < 1) {
return null;
}
// Init of pseudo random number generator.
if (randGen == null) {
if (randGen == null) {
randGen = new java.util.Random();
// Also initialize the numbersAndLetters array
numbersAndLetters = ("0123456789").toCharArray();
}
}
// Create a char buffer to put random letters and numbers in.
char[] randBuffer = new char[length];
for (int i = 0; i < randBuffer.length; i++) {
randBuffer[i] = numbersAndLetters[randGen.nextInt(9)];
}
return new String(randBuffer);
}

String number = "";
Random rd = new Random();
while (number.length() != 10) {
String rn = rd.nextInt(10) + "";
if (number.indexOf(rn) == -1)
number += rn;
}
System.out.println(number);
望采纳！