【反射】基于反射的实际应用——任意对象数组的排序 - 黑马程序员技术交流社区

class Cat
{
public int age = 1;
}

复制代码

Cat cat = new Cat();
System.out.println(cat.getClass().getField("age").get(cat));

复制代码

class Cat
{
private int age = 1;
public Cat()
{
}
public Cat(int age)
{
this.age = age;
}
public int getAge()
{
return age;
}
}

复制代码

Cat cat = new Cat();
System.out.println(cat.getClass().getMethod("getAge").invoke(cat));

复制代码

(double)cat.getClass().getMethod("getAge").invoke(cat)

复制代码

Double.parseDouble(cat.getClass().getMethod("getAge").invoke(cat).toString())

复制代码

Cat[] cats = {new Cat(100),new Cat(150),new Cat(50)};
for (Cat cat : cats)
{
System.out.println(Double.parseDouble(cat.getClass().getMethod("getAge").invoke(cat).toString()));
}

复制代码

class Wolf
{
public int age = 10;
public Wolf()
{
}
public Wolf(int age)
{
this.age = age;
}
public int getAge()
{
return age;
}
public String toString()
{
return ""+age;
}
}
class Cat
{
private int age = 1;
public Cat()
{
}
public Cat(int age)
{
this.age = age;
}
public int getAge()
{
return age;
}
public String toString()
{
return ""+age;
}
}
Object[] objects = {new Wolf(100),new Cat(150),new Cat(50)};
for (Object object : objects)
{
System.out.println(Double.parseDouble(object.getClass().getMethod("getAge").invoke(object).toString()));
}

复制代码

import java.lang.reflect.InvocationTargetException;
class Wolf
{
public int age = 10;
public Wolf()
{
}
public Wolf(int age)
{
this.age = age;
}
public int getAge()
{
return age;
}
public String toString()
{
return ""+age;
}
}
class Cat
{
public int age = 1;
public Cat()
{
}
public Cat(int age)
{
this.age = age;
}
public int getAge()
{
return age;
}
public String toString()
{
return ""+age;
}
}
public class lll
{
public static final boolean FROM_SMALL_TO_LARGE = true;
public static final boolean FROM_LARGE_TO_SMALL = false;
public static void main(String[] args) throws SecurityException, IllegalArgumentException, NoSuchFieldException, IllegalAccessException, NoSuchMethodException, InvocationTargetException
{
Object[] objects = {new Wolf(15), new Cat(20), new Wolf(), new Cat()};
for (Object object : objects)
{
System.out.println(object.toString());
}
bubbleSort(objects, "getAge()", FROM_SMALL_TO_LARGE);
System.out.println("===============================>");
for (Object object : objects)
{
System.out.println(object.toString());
}
System.out.println("===============================>");
bubbleSort(objects, "age", FROM_LARGE_TO_SMALL);
for (Object object : objects)
{
System.out.println(object.toString());
}
}
public static void bubbleSort(Object[] src, String expression, boolean is) throws NumberFormatException, IllegalArgumentException, SecurityException, IllegalAccessException, NoSuchFieldException, InvocationTargetException, NoSuchMethodException
{
int index = expression.indexOf("()");
if(index != -1)
{
expression = expression.substring(0, index);
}
double a,b;
for (int i = 0; i < src.length; ++i)
{
for (int j = 0; j < src.length - i - 1; ++j)
{
if(index != -1)
{
a = Double.parseDouble(src[j].getClass().getMethod(expression).invoke(src[j]).toString());
b = Double.parseDouble(src[j+1].getClass().getMethod(expression).invoke(src[j+1]).toString());
}
else
{
a = Double.parseDouble(src[j].getClass().getField(expression).get(src[j]).toString());
b = Double.parseDouble(src[j+1].getClass().getField(expression).get(src[j+1]).toString());
}
if(is && a > b)
{
swap(src, j, j+1);
}
else if(!is && a < b)
{
swap(src, j, j+1);
}
}
}
}
public static void swap(Object[] data, int i, int j)
{
Object temp = data[i];
data[i] = data[j];
data[j] = temp;
}
}

复制代码

15
20
10
1
===============================>
1
10
15
20
===============================>
20
15
10
1

复制代码