关于StringBuilder 的 请高手 解答！解决办法

public StringBuilder(int capacity) {    super(capacity);}AbstractStringBuilder(int capacity) {        value = new char[capacity];}public StringBuilder(String str) {    super(str.length() + 16);    append(str);}public StringBuilder append(String str) {    super.append(str);        return this;}public AbstractStringBuilder append(String str) {    if (str == null) str = "null";        int len = str.length();    if (len == 0) return this;    int newCount = count + len;    if (newCount > value.length)        expandCapacity(newCount);    str.getChars(0, len, value, count);    count = newCount;    return this;}虽然走的路不一样，最终的结果是一样的。
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Java code
public StringBuilder() {    super(16);}
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你可以看StringBuilder的源码，默认空的构造方法 是将StringBuilder的容量capacity设置为16 然后返回对象实例，以String为参数的构造方法是构造一个capacity为字符串长度+16的对象，然后将 String字符串append进去，

对于你说的这两者因为String为""长度为0，所以效果一样，不过这个多执行了一步append方法而已
Java code
public StringBuilder() {        super(16);    }  /**     * Constructs a string builder with no characters in it and an     * initial capacity specified by the <code>capacity</code> argument.     *     * @param      capacity  the initial capacity.     * @throws     NegativeArraySizeException  if the <code>capacity</code>     *               argument is less than <code>0</code>.     */    public StringBuilder(int capacity) {        super(capacity);    }