简单的StringBuffer实现

package com.letv.test.base;

import java.util.Arrays;

public class StringBuffer {
    private char[] value;
    private int count;

    public StringBuffer() {
        value = new char[16];
        count = 0;
    }

    public StringBuffer(String str) {
        value = Arrays.copyOf(str.toCharArray(), str.length() + 16);
        count = str.length();
    }

    public synchronized StringBuffer appen(String str) {
        if (count + str.length() > value.length) {
            value = Arrays.copyOf(value, count + str.length() + 16);
        }
        System.arraycopy(str.toCharArray(), 0, value, count, str.length());
        // str.getChars(0, str.length(), value, count);
        count = count + str.length();
        return this;
    }
}