package code.structures;public class Stack {private String[] s;// 用数组来模拟private int top;private int length;// 初始化public Stack(int index){this.s = new String[index];this.top = 0;this.length = index;}// 放数据public void push(String str){if(str == null){return;}if(top == length){System.out.println("stack is full");return;}this.s[top] = str;this.top++;}// 拿数据public String pop(){if(this.isEmpty()){System.out.println("There is no data");return null;}String s1 = s[--top];//因为数组从0开始，顺便每pop一次要把top减一s[top] = null;return s1;}// 取得最高位置public int getTop(){return this.top;}public boolean isEmpty(){if(this.top == 0){return true;}return false;}
}

package code.structures;public class Queue {private String[] s;// 用数组来模拟private int head; // 队列头private int tail; // 队列尾private int length; // 队列长度private boolean isFull; // 满信号private boolean isEmpty; // 空信号public Queue(int index) {this.s = new String[index];this.head = 0;this.tail = 0;length = index;isFull = false;isEmpty = true;}// 放数据public boolean enQueue(String str) {if (isFull) { // 已满的队列就不能再放数据啦System.out.println("queue is full");return false;}// 放在队列的尾部s[tail] = str;tail++; // 移动尾部// 头尾相连if (tail == length) {tail = 0;}// 在放数据的时候出现头尾相同时，就认为是满了if (head == tail) {isFull = true;}// 因为是放数据，所以不可能出现空队列if (isEmpty) {isEmpty = false;}return true;}// 拿数据public String deQueue() {if (isEmpty) {// 空队列就不处理了System.out.println("queue is empty");return null;}// 从头部取得数据String str = s[head];head++;if (head == length) {head = 0;}// 取数据的时候出现头尾相同，就认为出现空队列if (head == tail) {isEmpty = true;}// 因为是取数据，所以不可能出现一个满队列if (isFull) {isFull = false;}return str;}public boolean isEmpty(){return isEmpty;}public boolean isFull(){return isFull;}
}

    public ArrayList(int initialCapacity) {super();if (initialCapacity < 0)throw new IllegalArgumentException("Illegal Capacity: "+initialCapacity// 传入ArrayList大小，就帮你创建一个这样大小的Object数组this.elementData = (E[])new Object[initialCapacity];}public ArrayList() {this(10);//默认的话，就是10大小的数组}

 public void ensureCapacity(int minCapacity) {modCount++;int oldCapacity = elementData.length;if (minCapacity > oldCapacity) {Object oldData[] = elementData;// 新数组长度是老数组的1.5倍int newCapacity = (oldCapacity * 3)/2 + 1;if (newCapacity < minCapacity)newCapacity = minCapacity;// 创建出新的数组elementData = (E[])new Object[newCapacity];// 把老数据拷贝到新数组里去System.arraycopy(oldData, 0, elementData, 0, size);}}public boolean add(E o) {ensureCapacity(size + 1);  // 确定是否需要增长数组elementData[size++] = o;return true;}

       public E remove(int index) {RangeCheck(index);modCount++;E oldValue = elementData[index];//删除的数据作为返回值int numMoved = size - index - 1;if (numMoved > 0)// 用一个自我拷贝，移动了删除点后的全部数据，所以会影响效率System.arraycopy(elementData, index+1, elementData, index,numMoved);// copy数据后，最后一位的数据还在，需要把它删除elementData[--size] = null; // Let gc do its workreturn oldValue;}

select classId, count(case when sex = "男" then 1 end) from Test group by classTd;