Stringbuffer_append方法

Arrays

数组拷贝

arraycopy

private void ensureCapacityInternal(int minimumCapacity) { // overflow-conscious code if (minimumCapacity - value.length 0) expandCapacity(minimumCapacity); }

确保容量，判断是否需要扩容

String

private AbstractStringBuilder appendNull() { int c = count; ensureCapacityInternal(c + 4); final char[] value = this.value; value[c++] = 'n'; value[c++] = 'u'; value[c++] = 'l'; value[c++] = 'l'; count = c; return this; }

append(String str)

完成拷贝

AbstractStringBuilder

扩容

追加null

copyOf

StringBuffer

System

return this

调用ensureCapacityInternal，确保容量完成

getChars