我需要创建一个长度在 6 到 10 之间的随机字符串，但有时它只生成大约 3 到 5 的长度。
这是我的代码。任何人都可以找出问题所在吗？ :(
int lengthOfName = (int)(Math.random() * 4) + 6;
String name = "";
/* randomly choosing a name*/
for (int j = 0; j <= lengthOfName; j++) {
int freq = (int)(Math.random() * 100) + 1;
if(freq <= 6){
name += "a";
}if(freq == 7 && freq == 8){
name += "b";
}if(freq >= 9 && freq <= 11){
name += "c";
}if(freq >= 12 && freq <= 15){
name += "d";
}if(freq >= 16 && freq <= 25){
name += "e";
}if(freq == 26 && freq == 27){
name += "f";
}if(freq == 28 && freq == 29){
name += "g";
}if(freq >= 30 && freq <= 33){
name += "h";
}if(freq >= 34 && freq <= 48){
name += "i";
}if(freq == 49 && freq == 50){
name += "j";
}if(freq >= 51 && freq <= 55){
name += "k";
}if(freq >= 56 && freq <= 60){
name += "l";
}if(freq == 61 && freq == 62){
name += "m";
}if(freq >= 63 && freq <= 70){
name += "n";
}if(freq >= 71 && freq <= 75){
name += "o";
}if(freq == 76 && freq == 77){
name += "p";
}if(freq == 78){
name += "q";
}if(freq >= 79 && freq <= 84){
name += "r";
}if(freq == 85 && freq == 86){
name += "s";
}if(freq == 87 && freq == 88){
name += "t";
}if(freq >= 89 && freq <= 93){
name += "u";
}if(freq == 94){
name += "v";
}if(freq == 95 && freq == 96){
name += "w";
}if(freq == 97){
name += "x";
}if(freq == 98 && freq == 99){
name += "y";
}if(freq == 100){
name += "z";
}
}
抱歉，代码写得太差，无法挽救。我推荐这样的东西。
Random r = new Random(); // just create one and keep it around
String alphabet = "abcdefghijklmnopqrstuvwxyz";
final int N = 10;
StringBuilder sb = new StringBuilder();
for (int i = 0; i < N; i++) {
sb.append(alphabet.charAt(r.nextInt(alphabet.length())));
}
String randomName = sb.toString();
System.out.println(randomName);
要点是：
- Use java.util.Random http://java.sun.com/javase/6/docs/api/java/util/Random.html, specifically
nextInt(int n) to get a random int in a given range
- 在循环中构建字符串时，使用
StringBuilder.
- 使用字母字符串，并且
charAt来索引它的字母。
API链接
-
java.util.Random http://java.sun.com/javase/6/docs/api/java/util/Random.htmlhttp://java.sun.com/javase/6/docs/api/java/util/Random.html
-
int nextInt(int n) http://java.sun.com/javase/6/docs/api/java/util/Random.html#nextInt%28int%29
- 返回 0（含）和指定值（不含）之间均匀分布的伪随机 int 值
-
StringBuilder http://java.sun.com/javase/6/docs/api/java/lang/StringBuilder.html- 可变的字符序列。
相关问题
- 字符串与 StringBuilder (C#) https://stackoverflow.com/questions/73883/string-vs-stringbuilder
- 字符串、StringBuffer 和 StringBuilder (Java) https://stackoverflow.com/questions/2971315/string-stringbuffer-and-stringbuilder/
原来的代码有问题
不幸的是，有很多。
-
String +=对于较长的字符串，循环中的性能非常差
-
for (int j = 0; j <= lengthOfName; j++) is an 差一误差 http://en.wikipedia.org/wiki/Off-by-one_error
-
freq == 7 && freq == 8是一个逻辑矛盾
- It's just unnecessarily verbose!
我强烈建议做大量小而简单的练习来学习 Java 基础知识。编码蝙蝠网站 http://codingbat.com/java是很棒的;它有数百个，它们会自动评分，因此您会知道您的解决方案何时按预期工作。它有关于逻辑、字符串、数组等的部分。
关于字母分布不均匀
最简单的解决方案是在字母表中只包含重复项：
-
String alphabet = "aab";将有概率为a两倍b
- You can generate the
alphabet programmatically from a frequency table
- 我将把这个作为练习（或者如果你需要的话你可以问另一个问题）
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