实现方法

接口

public interface Calculator {

    public int add(int i, int j);

    public int sub(int i, int j);

    public int mult(int i, int j);

    public int div(int i, int j);
}

调用

public class CalculatorProxy {
    public static Calculator getProxy(final Calculator calculator){
        ClassLoader loader = calculator.getClass().getClassLoader();
        Class<?>[] interfaces = calculator.getClass().getInterfaces();
        InvocationHandler h = new InvocationHandler() {
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                Object result = null;
                try {
                    //接口的方法对象,通过发射调用实现类的方法。
                    result = method.invoke(calculator, args);
                } catch (Exception e) {
                } finally {
                }
                return result;
            }
        };
        Object proxy = Proxy.newProxyInstance(loader, interfaces, h);
        return (Calculator) proxy;
    }

    public static void main(String[] args) {
        System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");
        Calculator proxy = CalculatorProxy.getProxy(new MyCalculator());
        int add = proxy.add(1, 1);
        System.out.println(add);
        System.out.println(proxy.getClass());
    }
}

实现类

public class MyCalculator implements Calculator {
    public int add(int i, int j) {
        int result = i + j;
        return result;
    }

    public int sub(int i, int j) {
        int result = i - j;
        return result;
    }

    public int mult(int i, int j) {
        int result = i * j;
        return result;
    }

    public int div(int i, int j) {
        int result = i / j;
        return result;
    }
}

代理类文件。

public final class $Proxy0 extends Proxy implements Calculator {
    private static Method m1;
    private static Method m2;
    private static Method m3;
    private static Method m6;
    private static Method m4;
    private static Method m5;
    private static Method m0;

    public $Proxy0(InvocationHandler var1) throws  {
        super(var1);
    }

    public final boolean equals(Object var1) throws  {
        try {
            return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
        } catch (RuntimeException | Error var3) {
            throw var3;
        } catch (Throwable var4) {
            throw new UndeclaredThrowableException(var4);
        }
    }

    public final String toString() throws  {
        try {
            return (String)super.h.invoke(this, m2, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    public final int add(int var1, int var2) throws  {
        try {
            return (Integer)super.h.invoke(this, m3, new Object[]{var1, var2});
        } catch (RuntimeException | Error var4) {
            throw var4;
        } catch (Throwable var5) {
            throw new UndeclaredThrowableException(var5);
        }
    }

    public final int sub(int var1, int var2) throws  {
        try {
            return (Integer)super.h.invoke(this, m6, new Object[]{var1, var2});
        } catch (RuntimeException | Error var4) {
            throw var4;
        } catch (Throwable var5) {
            throw new UndeclaredThrowableException(var5);
        }
    }

    public final int mult(int var1, int var2) throws  {
        try {
            return (Integer)super.h.invoke(this, m4, new Object[]{var1, var2});
        } catch (RuntimeException | Error var4) {
            throw var4;
        } catch (Throwable var5) {
            throw new UndeclaredThrowableException(var5);
        }
    }

    public final int div(int var1, int var2) throws  {
        try {
            return (Integer)super.h.invoke(this, m5, new Object[]{var1, var2});
        } catch (RuntimeException | Error var4) {
            throw var4;
        } catch (Throwable var5) {
            throw new UndeclaredThrowableException(var5);
        }
    }

    public final int hashCode() throws  {
        try {
            return (Integer)super.h.invoke(this, m0, (Object[])null);
        } catch (RuntimeException | Error var2) {
            throw var2;
        } catch (Throwable var3) {
            throw new UndeclaredThrowableException(var3);
        }
    }

    static {
        try {
            m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
            m2 = Class.forName("java.lang.Object").getMethod("toString");
            m3 = Class.forName("com.sx.Proxy.jdk.Calculator").getMethod("add", Integer.TYPE, Integer.TYPE);
            m6 = Class.forName("com.sx.Proxy.jdk.Calculator").getMethod("sub", Integer.TYPE, Integer.TYPE);
            m4 = Class.forName("com.sx.Proxy.jdk.Calculator").getMethod("mult", Integer.TYPE, Integer.TYPE);
            m5 = Class.forName("com.sx.Proxy.jdk.Calculator").getMethod("div", Integer.TYPE, Integer.TYPE);
            m0 = Class.forName("java.lang.Object").getMethod("hashCode");
        } catch (NoSuchMethodException var2) {
            throw new NoSuchMethodError(var2.getMessage());
        } catch (ClassNotFoundException var3) {
            throw new NoClassDefFoundError(var3.getMessage());
        }
    }
}