length与capacity

package javaBasic;

public class DifferenceLengthCapacity {
	public static void main(String[] args) {
		StringBuffer sb = new StringBuffer(7);//定义指定长度的字符串缓冲区变量
		sb.append("hey");
		System.out.println("length:"+sb.length());//3
		System.out.println("capacity:"+sb.capacity());//7
		System.out.println(sb.toString());
		
		sb.ensureCapacity(17);//设置容量为17
		System.out.println("length:"+sb.length());//3
		System.out.println("capacity:"+sb.capacity());//17
		System.out.println(sb.toString());
		
		sb.append("java");
		System.out.println("length:"+sb.length());//7
		System.out.println("capacity:"+sb.capacity());//17
		System.out.println(sb.toString());
	}
}