遍历树 栈的泛型实现 db操作 读写文件 代码

void preOrder(BiTree bt){
BiTree Stack[MAX_TREE_SIZE];
BiTree  p;
int top = 0;
if(bt == null)
return;
p= bt;
while(!(p==null && 0==top)){
while(p!= null){
visit(p.data);
if(top<MAX_TREE_SIZE-1){
Stack[top++] =p;
}else{
println("OutOfStack!");
return;
}
p = p.lchild;

}
if(top<= 0)
return;
else{
p = Stack[--top];
p= p.rchild;
}

}
}


void levelOrder(BiTree bt){
BiTree Queue[MAX_TREE_SIZE];
int front,rear;
if(bt ==null)
return;
front =-1;
rear =0;
Queue[rear] =bt;
while(front != rear){
visit(Queue[++front].data);
if(Queue[front].lchild != null){
Queue[++rear] = Queue[front].lchild;
}
if(Queue[front].rchild != null){
Queue[++rear] = Queue[front].rchild;
}
}

}

 

 

public static boolean isPrime(int num) {
boolean prime = true;

if(num ==2 || num == 3)

return prime;

int limit = (int) Math.sqrt(num);

 for (int i = 2; i <= limit; i++) {
 if (num % i == 0) {
 prime = false;
 break;
 }

 }
return prime;
}

 

 

public static int binarySearch(int[] a, int key) {
if(a.length==0)
return -1;


int low = 0;
int high = a.length-1;
int mid;


while(low<=high)
{
mid = (low+high)/2;


if(a[mid]==key)
return mid;


if(a[mid]>key)
high = mid-1;


if(a[mid]<key)
low = mid+1;
}
return -1;
}

 

import java.util.Arrays;




public class Stack<E> {

private E[] elements;
private int size =0;
private static final int DEAULT_CAPACITY =16;

public Stack(){
elements = (E[])new Object[DEAULT_CAPACITY];
}

public void push(E e){
ensureCapacity();
elements[size++]=e;
}

public E pop(){
if(0 == size){
throw new EmptyStackException();
}
E result = elements[--size];
elements[size] = null;
return result;
}
public E peek(){
if(0 == size){
throw new EmptyStackException();
}
E result = elements[size];
}
private void ensureCapacity(){
if(elements.length == size){
elements = Arrays.copyOf(elements, 2*size +1);
}
}


}

 

 

 

 

package com.bjsxt.bbs;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DB {
 public static Connection getConn() {
  Connection conn = null;
  try {
   Class.forName("com.mysql.jdbc.Driver");
   conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/bbs", "root" , "root");
  } catch (ClassNotFoundException e) {
   e.printStackTrace();
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return conn;
 }
 
 public static Statement createStmt(Connection conn) {
  Statement stmt = null;
  try {
   stmt = conn.createStatement();
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return stmt;
 }
 
 public static ResultSet executeQuery(Statement stmt, String sql) {
  ResultSet rs = null;
  try {
   rs = stmt.executeQuery(sql);
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return rs;
 }
 
 /*public static ResultSet executeQuery(Connection conn, String sql) {
  Statement stmt = null;
  ResultSet rs = null;
  try {
   stmt = conn.createStatement();
   rs = stmt.executeQuery(sql);
  } catch (SQLException e) {
   e.printStackTrace();
  }
  
//  finally {
//   close(stmt);
//  }
  
  
  return rs;
 }*/
 
 public static int executeUpdate(Connection conn, String sql) {
  int ret = 0;
  Statement stmt = null;
  try {
   stmt = conn.createStatement();
   ret = stmt.executeUpdate(sql);
  } catch (SQLException e) {
   e.printStackTrace();
  } finally {
   close(stmt);
  }
  return ret;
 }
 
 public static PreparedStatement prepareStmt(Connection conn, String sql) {
  PreparedStatement pstmt = null;
  try {
   pstmt = conn.prepareStatement(sql);
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return pstmt;
 }
 
 public static PreparedStatement prepareStmt(Connection conn, String sql, int autoGeneratedKeys) {
  PreparedStatement pstmt = null;
  try {
   pstmt = conn.prepareStatement(sql, autoGeneratedKeys);
  } catch (SQLException e) {
   e.printStackTrace();
  }
  return pstmt;
 }
 
 public static void close(Connection conn) {
  if(conn != null) {
   try {
    conn.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
   conn = null;
  }
 }
 
 public static void close(Statement stmt) {
  if(stmt != null) {
   try {
    stmt.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
   stmt = null;
  }
 }
 
 public static void close(ResultSet rs) {
  if(rs != null) {
   try {
    rs.close();
   } catch (SQLException e) {
    e.printStackTrace();
   }
   rs = null;
  }
 }
}

public class TextFile extends ArrayList<String> {
  // Read a file as a single string:
  public static String read(String fileName) {
    StringBuilder sb = new StringBuilder();
    try {
      BufferedReader in= new BufferedReader(new FileReader(
        new File(fileName).getAbsoluteFile()));
      try {
        String s;
        while((s = in.readLine()) != null) {
          sb.append(s);
          sb.append("\n");
        }
      } finally {
        in.close();
      }
    } catch(IOException e) {
      throw new RuntimeException(e);
    }
    return sb.toString();
  }
  // Write a single file in one method call:
  public static void write(String fileName, String text) {
    try {
      PrintWriter out = new PrintWriter(
        new File(fileName).getAbsoluteFile());
      try {
        out.print(text);
      } finally {
        out.close();
      }
    } catch(IOException e) {
      throw new RuntimeException(e);
    }
  }