橋接模式(Bridge)
先定義接口:
public interface Sourceable {
public void method();
}
public class SourceSub1 implements Sourceable {
@Override
public void method() {
System.out.println("this is the first sub!");
}
}
public class SourceSub2 implements Sourceable {
@Override
public void method() {
System.out.println("this is the second sub!");
}
}
定義一個橋,持有Sourceable的一個實例:public abstract class Bridge {
private Sourceable source;
public void method(){
source.method();
}
public Sourceable getSource() {
return source;
}
public void setSource(Sourceable source) {
this.source = source;
}
}
public class MyBridge extends Bridge {
public void method(){
getSource().method();
}
}
public class BridgeTest {
public static void main(String[] args) {
Bridge bridge = new MyBridge();
/*調用第一個對象*/
Sourceable source1 = new SourceSub1();
bridge.setSource(source1);
bridge.method();
/*調用第二個對象*/
Sourceable source2 = new SourceSub2();
bridge.setSource(source2);
bridge.method();
}
}
output:this is the first sub!
this is the second sub!
這樣,就通過對Bridge類的調用,實現了對接口Sourceable的實現類SourceSub1和SourceSub2的調用。
組合模式(Composite)
組合模式有時又叫部分-整體模式在處理類似樹形結構的問題時比較方便public class TreeNode {
private String name;
private TreeNode parent;
private Vector<TreeNode> children = new Vector<TreeNode>();
public TreeNode(String name){
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public TreeNode getParent() {
return parent;
}
public void setParent(TreeNode parent) {
this.parent = parent;
}
//添加孩子節點
public void add(TreeNode node){
children.add(node);
}
//刪除孩子節點
public void remove(TreeNode node){
children.remove(node);
}
//取得孩子節點
public Enumeration<TreeNode> getChildren(){
return children.elements();
}
}
public class Tree {
TreeNode root = null;
public Tree(String name) {
root = new TreeNode(name);
}
public static void main(String[] args) {
Tree tree = new Tree("A");
TreeNode nodeB = new TreeNode("B");
TreeNode nodeC = new TreeNode("C");
nodeB.add(nodeC);
tree.root.add(nodeB);
System.out.println("build the tree finished!");
}
}
使用場景:將多個對象組合在一起進行操作,常用於表示樹形結構中,例如二叉樹,數等。享元模式(Flyweight)
public class ConnectionPool {
private Vector<Connection> pool;
/*公有屬性*/
private String url = "jdbc:mysql://localhost:3306/test";
private String username = "root";
private String password = "root";
private String driverClassName = "com.mysql.jdbc.Driver";
private int poolSize = 100;
private static ConnectionPool instance = null;
Connection conn = null;
/*構造方法,做一些初始化工作*/
private ConnectionPool() {
pool = new Vector<Connection>(poolSize);
for (int i = 0; i < poolSize; i++) {
try {
Class.forName(driverClassName);
conn = DriverManager.getConnection(url, username, password);
pool.add(conn);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
/* 返回連接到連接池 */
public synchronized void release() {
pool.add(conn);
}
/* 返回連接池中的一個數據庫連接 */
public synchronized Connection getConnection() {
if (pool.size() > 0) {
Connection conn = pool.get(0);
pool.remove(conn);
return conn;
} else {
return null;
}
}
}
通過連接池的管理,實現了數據庫連接的共享,不需要每一次都重新創建連接,節省了數據庫重新創建的開銷,提升了系統的性能!第一類:通過父類與子類的關係進行實現。第二類:兩個類之間。第三類:類的狀態。第四類:通過中間類