StringBuilder

StringBuilder bu = new StringBuilder();       StringBuilder bu2 = new StringBuilder();       StringBuilder bu4 = bu.append("cbd");       StringBuilder bu3 = bu.append("cbd");       bu.append(true);       System.out.println(bu);       System.out.println(bu2);                       String s = bu.toString();               public static void main(String[] args) {   // 构建StringBuilder对象   StringBuilder bu = new StringBuilder();// "" 0   // 调用insert方法   【System.out.println(bu.length());】   /*         if ((offset < 0) || (offset > length()))             throw new StringIndexOutOfBoundsException(offset);     */   【StringBuilder bu2 = bu.insert(0, "A");】   System.out.println(bu2);   System.out.println(bu == bu2);   System.out.println(bu2.length());   bu.insert(1, "B");   System.out.println("bu2:" + bu2);   // 插入一个布尔类型值   bu.insert(2, true);   System.out.println(bu);   System.out.println("bu字符串缓冲区的长度为：" + bu.length());   System.out.println("bu字符串缓冲区的容量大小为：" + bu.capacity());   Student student = new Student();   student.setAge(10);   student.setName("小王");   bu.insert(6, student);   System.out.println("=");   System.out.println(bu.length());   System.out.println(bu);   System.out.println("=");   【System.out.println(bu.capacity());// miniCapacity.lenght()】Integer.MAX_VALUE < minCapacity   // throw