浅谈StringBuffer的capacity()方法

java.lang.StringBuffer.capacity()方法返回当前容量。 容量是新插入字符可用的存储量，超出该容量将进行分配。

以下是java.lang.StringBuffer.capacity()方法的声明

public int capacity()

Null

该方法返回当前容量

public class CapacityTest {
	public static void main(String[] args) {
		StringBuffer sb = new StringBuffer();//默认容量为16
		int originalLength = sb.length();
		System.out.println("The initialization capacity is : " + sb.capacity());//初始容量即默认容量为16
		int originalCapacity = sb.capacity();
		sb.append("I am Jack.Nice to meet you!");//将指定的字符串追加到此字符序列
		System.out.println("The string to be added : " + "I am Jack.Nice to meet you!" );
		System.out.println("The length of the string to be added is : " + sb.length());//串长
		int minimum_capacity = originalLength + sb.length();
		System.out.println("The minimum capacity is : " + minimum_capacity);//最小容量 = 将要append(s)前的长度+ 将要append(s)中的s的串长
		int proposedCapacityExpansion = (originalCapacity + 1) * 2;
		System.out.println("New capacity to be expanded : " + proposedCapacityExpansion); //拟扩充的新容量 = (旧容量 + 1) * 2 
		if(minimum_capacity <= proposedCapacityExpansion) 
		{//如果最小容量不大于拟扩充的新容量，则以拟扩充的新容量进行扩充
			System.out.println("The expansion of appended characters is expanded according to the new elements to be expanded");
		}
		else 
		{//如果最小容量大于拟扩充的新容量，则以最小容量进行扩充
			System.out.println("The expansion of appended characters is expanded according to the minimum capacity of the proposed expansion");
		}
	}
}

拟扩充的新容量 = (旧容量 + 1) * 2 ，最小容量 = 将要append(s)前的长度+ 将要append(s)中的s的串长。如果拟扩充的新容量>=最小容量，则按照拟扩充的新容量进行扩充；否则按照最小容量进行扩充。

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