使用了泛型类和没使用泛型类的小例子对比

使用了泛型类：

class Gen<T>
{
    private T ob;     //定义泛型成员变量
    public Gen(T ob)
    {
        this.ob = ob;
    }
    public T getOb()
    {
        return ob;
    }
    public void setOb(T ob)
    {
        this.ob = ob;
    }
    public void showType()
    {
        System.out.println("T的实际类型是:" + ob.getClass().getName());
    }
}

public class JustTest
{
    public static void main(String[] args)
    {
        Gen<Integer> intOb = new Gen<Integer>(88);
        intOb.showType();
        int i  = intOb.getOb();
        System.out.println("value = " + 1);
        System.out.println("----------------");
        Gen<String> strOb = new Gen<String>("Hello JustTest");
        strOb.showType();
        String s = strOb.getOb();
        System.out.println("value = " + s);
    }
}

没有使用泛型类：

class Gen2
{
    private Object ob;   //定义一个通用类型行为
    public Gen2(Object ob)
    {
        this.ob = ob;
    }
    public Object getOb()
    {
        return ob;
    }
    public void setOb(Object ob)
    {
        this.ob = ob;
    }
    public void showType()
    {
        System.out.println("T的实际类型是:" + ob.getClass().getName());
    }
    
}
public class SecTest 
{
    public static void main(String[] args)
    {
        Gen2 intOb = new Gen2(new Integer(88));
        intOb.showType();
        int i = (Integer)intOb.getOb();
        System.out.println("value = " + i);
        System.out.println("--------------");
        Gen2 strOb = new Gen2("Hello World");
        strOb.showType();
        String s = (String) strOb.getOb();
        System.out.println("Vale = " + s );
    }

}