一、单例模式

1. 饱汉模式

   public class SinglePattern2 {
   	
   	private SinglePattern2 sp;
   
   	public SinglePattern2 getInstance() {
   		if (sp == null) {
   			return new SinglePattern2();
   		}
   		return sp;
   	}
   }
2. 饿汉模式

   public class SinglePattern1 {
   	
   	private SinglePattern1 sp = new SinglePattern1();
   
   	public SinglePattern1 getInstance() {
   		return sp;
   	}
   }
   

   两种模式差别在有没有在类被加载时就给创建好对象，‘饿汉’ 即等不及了要吃东西所以要提前创建好对象，‘饱汉’正好相反

二、模板方法

给出算法的骨架，具体由实现类去实现。

public abstract class Account {

	private int year;
	private double fund;

	
	public Account(int year, double fund) {
		super();
		this.year = year;
		this.fund = fund;
	}

	public int getYear() {
		return year;
	}

	public void setYear(int year) {
		this.year = year;
	}

	public double getFund() {
		return fund;
	}

	public void setFund(double fund) {
		this.fund = fund;
	}

	// 具体账户计算所获得信息必须先实现该账户的利率
	public double getInterest() {
		return fund * getInterestRate();
	}

	public abstract double getInterestRate();
}

public class AccountA extends Account {
	private static final double INTEREST = 0.03; 
	
	public AccountA(int year, double fund) {
		super(year, fund);
	}

	@Override
	public double getInterestRate() {
		return super.getYear() * INTEREST;
	}
}

public class Test {
	public static void main(String[] args) {
		AccountA a = new AccountA(3,20000);
		System.out.println(a.getInterest());
	}
}