Factory Design Pattern 工厂设计模式（工厂方法设计模式）

package com.sheting.design.pattern.demo1;

public abstract class Computer {

    public abstract String getRAM();
    public abstract String getHDD();
    public abstract String getCPU();

    @Override
    public String toString(){
        return "RAM= "+this.getRAM()+", HDD="+this.getHDD()+", CPU="+this.getCPU();
    }

}

package com.sheting.design.pattern.demo1;

public class PC extends Computer {

    private String ram;
    private String hdd;
    private String cpu;

    public PC(String ram, String hdd, String cpu) {
        this.ram = ram;
        this.hdd = hdd;
        this.cpu = cpu;
    }

    @Override
    public String getRAM() {
        return this.ram;
    }

    @Override
    public String getHDD() {
        return this.hdd;
    }

    @Override
    public String getCPU() {
        return this.cpu;
    }

}

package com.sheting.design.pattern.demo1;

public class Server extends Computer {
    private String ram;
    private String hdd;
    private String cpu;

    public Server(String ram, String hdd, String cpu) {
        this.ram = ram;
        this.hdd = hdd;
        this.cpu = cpu;
    }

    @Override
    public String getRAM() {
        return this.ram;
    }

    @Override
    public String getHDD() {
        return this.hdd;
    }

    @Override
    public String getCPU() {
        return this.cpu;
    }

}

package com.sheting.design.pattern.demo1;

public class ComputerFactory {

    public static Computer getComputer(String type, String ram, String hdd, String cpu) {
        if ("PC".equalsIgnoreCase(type)) {
            return new PC(ram, hdd, cpu);
        } else if ("Server".equalsIgnoreCase(type)) {
            return new Server(ram, hdd, cpu);
        }

        return null;
    }

}

package com.sheting.design.pattern.demo1;

public class TestFactory {

    public static void main(String[] args) {
        Computer pc = ComputerFactory.getComputer("pc", "2 GB", "500 GB", "2.4 GHz");
        Computer server = ComputerFactory.getComputer("server", "16 GB", "1 TB", "2.9 GHz");
        System.out.println("Factory PC Config::" + pc);
        System.out.println("Factory Server Config::" + server);
    }
}

JDK中的工厂方法模式

1. java.text.NumberFormat

private static NumberFormat getInstance(LocaleProviderAdapter adapter,
                                            Locale locale, int choice) {
        NumberFormatProvider provider = adapter.getNumberFormatProvider();
        NumberFormat numberFormat = null;
        switch (choice) {
        case NUMBERSTYLE:
            numberFormat = provider.getNumberInstance(locale);
            break;
        case PERCENTSTYLE:
            numberFormat = provider.getPercentInstance(locale);
            break;
        case CURRENCYSTYLE:
            numberFormat = provider.getCurrencyInstance(locale);
            break;
        case INTEGERSTYLE:
            numberFormat = provider.getIntegerInstance(locale);
            break;
        }
        return numberFormat;
    }

2. 包装类中的valueOf()

java.lang.Integer

public static Integer valueOf(int i) {
        if (i >= IntegerCache.low && i <= IntegerCache.high)
            return IntegerCache.cache[i + (-IntegerCache.low)];
        return new Integer(i);
}

public static Integer valueOf(String s) throws NumberFormatException {
        return Integer.valueOf(parseInt(s, 10));
}

 public static Integer valueOf(String s, int radix) throws NumberFormatException {
        return Integer.valueOf(parseInt(s,radix));
}