Assert

package com.sina.util;

import java.util.Collection;
import java.util.Map;

public abstract class Assert
{

    public Assert()
    {
    }

    public static void isTrue(boolean expression, String message)
    {
        if(!expression)
            throw new IllegalArgumentException(message);
        else
            return;
    }

    public static void isTrue(boolean expression)
    {
        isTrue(expression, "[Assertion failed] - this expression must be true");
    }

    public static void isNull(Object object, String message)
    {
        if(object != null)
            throw new IllegalArgumentException(message);
        else
            return;
    }

    public static void isNull(Object object)
    {
        isNull(object, "[Assertion failed] - the object argument must be null");
    }

    public static void notNull(Object object, String message)
    {
        if(object == null)
        {
            if(message == null)
                message = (new StringBuilder()).append("[Assertion failed] - this argument is required; it cannot be null. <").append(inferCaller()).append(">").toString();
            throw new IllegalArgumentException(message);
        } else
        {
            return;
        }
    }

    public static void notNull(Object object)
    {
        notNull(object, null);
    }

    private static String inferCaller()
    {
        StackTraceElement stack[] = (new Throwable()).getStackTrace();
        for(int i = 0; i < stack.length; i++)
        {
            StackTraceElement frame = stack[i];
            String cname = frame.getClassName();
            if(!cname.equals(Assert.getName()))
                return (new StringBuilder()).append(cname).append(".").append(frame.getMethodName()).toString();
        }

        return "";
    }

    public static void isInstanceOf(Class clazz, Object obj)
    {
        isInstanceOf(clazz, obj, "");
    }

    public static void isInstanceOf(Class clazz, Object obj, String message)
    {
        notNull(clazz, "The clazz to perform the instanceof assertion cannot be null");
        isTrue(clazz.isInstance(obj), (new StringBuilder()).append(message).append("Object of class '").append(obj == null ? "[null]" : obj.getClass().getName()).append("' must be an instance of '").append(clazz.getName()).append("'").toString());
    }

    public static void notNullOrEmpty(Object object)
    {
        notNullOrEmpty(object, null);
    }

    public static void notNullOrEmpty(Object object, String message)
    {
        notNull(object, null);
        if((object instanceof String) && ((String)object).trim().equals(""))
        {
            if(message == null)
                message = (new StringBuilder()).append("[Assertion failed] - this String argument is required; it cannot be empty. <").append(inferCaller()).append(">").toString();
            throw new IllegalArgumentException(message);
        }
        if((object instanceof Collection) && ((Collection)object).isEmpty())
        {
            if(message == null)
                message = (new StringBuilder()).append("[Assertion failed] - this Collection argument is required; it cannot be empty. <").append(inferCaller()).append(">").toString();
            throw new IllegalArgumentException(message);
        }
        if((object instanceof Map) && ((Map)object).isEmpty())
        {
            if(message == null)
                message = (new StringBuilder()).append("[Assertion failed] - this Map argument is required; it cannot be empty. <").append(inferCaller()).append(">").toString();
            throw new IllegalArgumentException(message);
        } else
        {
            return;
        }
    }
}