实现输出字符串的长度，容量（容量不够则扩容），及内容
import java.util.Arrays;
public class MyStringBuilderDemo {
//任务：存储字符串并输出长度及容量
public static void main(String[] args) {
// TODO Auto-generated method stub
MyStringBuilder msb = new MyStringBuilder();
msb.append("hello").append(",java").append("1234567");
System.out.println("字符串长度："+msb.length());
System.out.println("字符串容量："+msb.capacity());
System.out.println("输出字符串："+msb.toString());
}
}
class MyStringBuilder{
private char[] value;//字符串的值
private int count;//字符串的长度
public int length() {
return count;
}
public int capacity() {
return value.length;
}
public MyStringBuilder(){//默认给定数组容量为16
value = new char[16];
}
public MyStringBuilder(int capacity){//默认给定数组容量为16
value = new char[capacity];
}
//追加字符串
public MyStringBuilder append(String str) {
int len = str.length();
addength(count+len);
//追加字符串 追加的字符串.getChars(追加字符串的起始位置,结束为止,目标字符串,开始写入的位置)
str.getChars(0, str.length(), value, count);
count+=len;
return this;
}
private void addength(int capacity) {//防止字符串长度不够，扩容数组
if(capacity -value.length>0) {
int newlength;
newlength = value.length*2+2;
value = Arrays.copyOf(value, newlength);
}
}
//输出字符串
public String toString() {
return new String(value,0,count);
}
}