RealJavaScript

RJS (RealJavaScript) is the REAL Scripting language built for Java.

• RJS enables dynamic scripting in Java.
• Dynamic debugging in Java.
• Built on pure Java.
• Supports Android platform too.
• Things you thought can be done only on compile time can now be done in run time.

How to use RealJavaScript?

1. Include the RealJavaScript.jar as a library to your project.
2. Import com.zero1.realjavascript.RJSBridge to your Java class.
3. Use the RJSBridge.interpret() function to invoke RJS commands. Example:

import com.zero1.realjavascript.RJSBridge;  public class MyJavaClass {

int a, b = 10;
public static void main(String[] args) {

MyJavaClass myJavaClass = new MyJavaClass();

myJavaClass.doTheMagic();
  
}

public void doTheMagic() {

// RJS Script to print Hello World! Output: Hello World!
RJSBridge.interpret(this, "call java.lang.System.out.println \"Hello World!\"");

 // RJS Script to interact with your class fields. Output: 15
RJSBridge.interpret(this, "assign 5 to a and call java.lang.System.out.println (compute a+b)");

 // RJS Script to interact with your class methods. Output: Hello Sanju
RJSBridge.interpret(this, "call printHello \"Sanju\"");
  
}

void printHello(String name) {

System.out.println("Hello " + name);
  
}
 
}
 

RealJavaScript Syntax and Commands

GENERAL:

• All RJS Commands are case insensitive.

Example: call helloWorld is the same as CALL helloWorld. Both will call the method helloWorld from the calling object.

• Multiple commands can be executed in a linear fashion by separating the commands by using the AND keyword.

Example: call helloWorld and call java.lang.System.out.println 123 will execute the commands separated by and keyword from left to right. So at first, call helloWorld is executed and then call java.lang.System.out.println 123 is executed.

• Objects/Fields/Classes/Functions created using RJS commands can be accessed by prefixing the & symbol.

Example: create java.util.Date date and call java.lang.System.out.println &date will print the date object in the system console.

• An object's method can be accessed by using the dot operator '***.***'.

Example: create java.util.Date date and call java.lang.System.out.println &date.getTime will call getTime function of the created object named date.

• In RJS, string appending is similar to how it is in Java. The plus operator + is used for appending.

Example: call java.lang.System.out.println "The current time is "+(create java.util.Date date) will print the string "The current time is Sat Nov 19 23:09:35 IST 2016" in the system console.

• The plus operator + can also be used for appending part of command or keyword or text as well.

Example: Consider we have a method named getFalString which returns the string "fal" public void getFalString(){ return "fal" } now in RJS, if ((call getFalString)+se) then { call print 1 } else { call print 0 } will print the integer value 0 in the system console. In the If condition, the string returned from the method getFalString is appened with se which makes it false as a whole and thus the else part is executed. The strings when combined if makes sense, then it is understood by RJS. This type of appending is possible in RJS.

• RJS Commands can be nested within another command. If your nested command needs to execute only one RJS command, then enclose your command within the ( and ) braces. If your nested command needs to execute more than one RJS command, then enclose your commands within the { and } braces.

Example:
Nested single command: call java.lang.System.out.println (compute 10*(call funcToAdd2Nos (compute -1-3),9)) will execute call compute -1-3 first and the result -4 and 9 is passed as arguments for the function funcToAdd2Nos and the result which is 5 is executed with compute command. So here, the integer value 50 is printed in the system console. The execution order is from the inner most nested command to the outer command. If the command inside the ( ) braces, if the execution results in a value, it is returned to the outer command.

Nested multiple commands: call java.lang.System.out.println { create java.util.Date date and create java.lang.String dateString = call &date.toString and call &dateString.length } will execute commands from left to right inside the { } braces. Here an object named date is created for the class java.util.Date and another object named dateString of type java.lang.String is created and is assigned with the date object's toString method execution's result and then dateString object's length method is executed which is the last statement and this value is returned. So the integer value 11 is printed in the system console which is the length of the java.lang.String object named dateString. For commands inside { } braces, the last statement if is a value is returned to the outer command. In the above example, call &dateString.length is the last statement and thus the result of this command is returned to the outer command.

• null keyword can be used in RJS Script just the same way it is used in Java.

Example: java.lang.String myString=null; call java.lang.System.out.println (is myString==null) will print true in the system console.

• this keyword in RJS Script refers to the object passed to RJSBridge. The passed object is used for operations this is used in RJS.

Example: call this.print this.myVariable will call the the method named print by passing myVariable as parameter for that method. Here, both the method print and the variable myVariable belong to the object that was passed to RJSBridge. So this keyword refers to the object that was passed to RJSBridge and not the conventional Java's this.

• Numbers, Strings and boolean can be defined as done in Java.

Example: Numbers: compute 1+a, Here 1 is considered as java.lang.Integer. compute 1.5+a, here 1.5 is considered as java.lang.Float. Strings: call java.lang.System.out.println "Hello World!", in RJS, anything that is specified within double quotes is considered as java.lang.String. Boolean: if (is 2>1) then { true } else { false } . Here true is considered as boolean true and false is considered as boolean false.

• Logical Operations can be done through RJS.

Example: AND: call java.lang.System.out.println (is true && (is 1==2)) will print false as the second evaluation fails. In AND operation, if one of the evaluation results in false, then the other evaluations are not checked. OR call java.lang.System.out.println (is true || (is 1==2)) will print true and the second evaluation is not checked at all since this this an OR operation.

• To execute Logical operations for more than 2 evaluations, use nesting.

Example: call java.lang.System.out.println (is (is (is 8>3) && (is 2==2)) && (is 6<6)) will print false as 6<6 evaluation fails. This checks for 3 evaluations and only if all 3 are true, the result is true.

CALL:

• Used to call a method.

Example: call helloWorld will call the function named helloWorld from the calling object.

• Can call methods with parameters too.

Example: call funcToAdd2Nos 10,12 will call the function named funcToAdd2Nos by passing two integer parameters 10 and 12. The parameters are seperated using the , symbol.

• Returns object if the method returns anything.

Example: call print (call funcToAdd2Nos 10,12) will call the function named print by passing the result received by calling funcToAddNos 10, 12 which will be 22. So 22 is passed to the print function.

• Can call an object's method or a static method too.

Example: call java.lang.System.out.println "Hello World!" will call j ava.lang.System.out's println method by passing the string. "Hello World".

• Supports polymorphism.

Example: call exit and call exit 1. Here call exit calls the function named exit which does not accept any parameter. Whereas call exit 1 calls the function named exit which accepts one integer parameter.

• Negation of a function can be done. Used to negate the return value.

Example: call java.lang.System.out.println -(call funcToAdd2Nos 10,12) will print -22 in the console.

• Logical NOT on a function result can be done.

Example: call java.lang.System.out.println !false will print true in the console.

• Parameters can be variables, objects and direct numbers or strings too.

Example: call java.lang.System.out.println myVariable will call println function of java.lang.System.out by passing the variable named. myVariable.

COMPUTE:

• Used to perform mathematical calculations.

Example: compute 5 + 7 adds the numbers 5 and 7 and returns 12.

• Supports passing variables and direct numbers as parameters.

Example: compute 5 + myVariable adds the number 5 with the value stored in the variable myVariable and returns the computational result.

• Performs calculation using BODMAS technique.

Example: compute "a+b*c/(-4/b-1)" will return the result based on BODMAS technique.

• Can calculate more than 2 variables/numbers at the same time.

Example: compute "a*a+b*b+2*a*b" will perform the computation based on BODMAS technique. To perform computations on more than 2 variables/numbers, enclose the computation within double quotes.

• Supports Addition, Subtraction, Multiplication and Division.

Example: Addition: compute 3+5 will return the value 8. Subtraction: compute 3-5 will return the value -2. Multiplication: compute 3*5 will return the value 15. Division: compute 3/5 will return the value 0.6.

TO:

• Used to set the result of an operation to a variable or object.

Example: call funcToAdd2Nos 5, (compute 3+7) to b will call the method named funcToAdd2Nos by passing values 5 and the computational result by calling compute 3+7 and the result is assigned to the variable named b. So in this example, 15 is assigned to b.

ASSIGN:

• Used to assign a value (variable or object or direct number/string) to another variable or object.

Example: assign 5 to d will assign the value 5 to the variable named d.

CREATE:

• Used to create an object.

Example: create java.util.Date date will create a java.util.Date object with the name date.

• Can create local objects and other class' objects as well.

Example: create Tester tester will create an object for the local class Tester with the name tester.

• Created object can be assigned to other objects too.

Example: create java.util.Date date to myDateVariable will create a java.util.Date object with the name date and will be assigned to preexisting java.util.Date object named myDateVariable.

• Created objects can also be accessed within RJS script.

Example: create java.util.Date date creates a java.util.Date object named date. This object is created inside RJS. All objects created using RJS can be accessed by prefixing the & to the created object's name. Like, call java.lang.System.out.println &date will pass the date object to java.lang.System.out.println which will print the result in the system console.

• Constructor polymorphism supported.

Example: create java.util.Date date will create a java.util.Date object by passing no parameters. Whereas, create java.util.Date date 1479396430482 will create a java.util.Date object by passing one long parameter.

IS:

• Used to perform boolean operations.

Example: is a>b will evaluate if the value in a is greater than the value in b. The result will be a boolean true or false.

• Supports Equal To, Not Equal To, Greater Than, Lesser Than, Greater Than or Equal To, Lesser Than or Equal To.

Example: Equal To: is 5 == 3 will return boolean false. Not Equal To: is 5 != 3 will return boolean true. Greater Than: is 5 > 3 will return boolean true. Lesser Than: is 5 < 3 will return boolean false. Greater Than or Equal To: is 5 >= 3 will return boolean true. Lesser Than or Equal To: is 5 <= 3 will return boolean false.

IF, THEN, ELSE:

• Used to perform branching executions.

Example: if (is a>b) then { call java.lang.System.out.println \"Hello\" } else { call java.lang.System.out.println \"Bye\" } will evaluate is a>b and if the result is true, the then part will be executed. If the result is false, the else part will be executed.

• Else part is not mandatory.

Example: if (is a>b) then { call java.lang.System.out.println "Hello" } will evaluate is a>b and if the result is true, the then part will be executed. If the result is false, nothing is executed.

CLASS:

• Used to create an RJSClass.

Example: class myRJSClass fields <? java.lang.String string1,string2,string3="Sanju"; java.lang.Integer num = 123 ?> methods <? myMethod <@ java.lang.String name @> { call java.lang.System.out.println $name } ; myMethod <@ java.lang.String name, java.lang.Integer sno @> { call java.lang.System.out.println ($sno)+") "+($name) } ?> will create a RJS class named myRJSClass with three java.lang.String objects namely string1, string2 and string3 and one java.lang.Integer object named num. Here, the variable named string3 is assigned with the string "Sanju" and the variable named num is assigned with the value 123. Two methods named myMethod is created; one method accepts only one java.lang.String object and another method accepts one java.lang.String object and one java.lang.Integer object. The first method calls the println method of java.lang.System.out by passing the java.lang.String object passed to it while invoking myMethod. The second method calls the println method of java.lang.System.out by passing the java.lang.String and java.lang.Integer objects passed to it while invoking myMethod.

• RJSClass can have it's own fields.

Example: class myClass2 fields <? java.lang.String s1 ?> creates a RJS class named myClass2 with a field named s1 which is of type java.lang.String. Fields need to be mentioned after the fields keyword and the fields are to be declared/defined within the braces. RJS fields can be accessed within RJS methods of the same class without using the & symbol. class myRJSClass fields <? java.lang.String name = "Sanjeevi" ?> methods <? printMyName { call java.lang.System.out.println "Hello "+ (name) } ?> here a class named myRJSClass is created with one field named name and is assigned the string value "Sanjeevi" and the RJS method named printMyName can access the RJS field name without the & symbol. In this example, since we are doing string appending operation, the RJS field name is enclosed within ( ) braces. Multiple fields of the same type can be declared/defined using comma , to separate each field. Example: java.lang.String string1, string2 will create two java.lang.String objects named string1, string2 . Multiple fields of different types need to be declared/defined using semi colon ; as separator. Example: java.lang.String string1; java.lang.Integer num will create one java.lang.String object named string1 and one java.lang.Integer object named num.

• Fields can be preassigned.

Example: class myClass2 fields <? java.lang.String s1 = "Sanju" ?> will create a RJS class named myClass2 with a field named s1 of type java.lang.String and is assigned the string value "Sanju". RJS fields need to be assigned using the = symbol while creating them.

• RJSClass can have it's own methods.

Example: class myClass3 methods <? myMethod { call java.lang.System.out.println \"Hello World\" } ?> will create a class named myClass3 with one method named myMethod which accepts no parameters. Multiple RJS Methods can be defined using the semi colon ; as separator. Example: myMethod1 { call java.lang.System.out.println "No parameters" } ; myMethod2 <@ java.lang.Integer num @> { call java.lang.System.out.println $num } ?>. will create two methods named myMethod1 and myMethod2.

• Methods can have arguments.

Example: class myClass3 methods myMethod <@ java.lang.String firstName @> { call java.lang.System.out.println "Hello "+($firstName) } ?> will create a class named myClass3 with one method named myMethod which accepts one java.lang.String as parameter. The parameter firstName is accessed inside the method named myMethod by prefixing the parameter name with ***$***. RJS Methods may not accept any parameters. Example: myMethod { call java.lang.System.out.println "No parameters" } .

• Methods will return if it has anything to return.

Example: class myClass3 methods <? getGreatestNum <@ java.lang.Integer num1, java.lang.Integer num2 @> { if (is $num1>$num2) then { $num1 } else { $num2 } } ?> will create a class named myClass3 which has one method named getGreatestNum which accepts two java.lang.Integer arguments. The method evaluates which integer is greater and returns the greatest integer. The last statement in any method if is a value, is the value that is returned. Otherwise null is returned.

• Objects can be created for RJSClasses.

Example: create &myClass3 myObject and call java.lang.System.out.println (call &myObject.getGreatestNum 2,5) will create an object named myObject for the RJSClass myClass3. The method getGreatestNum is called by using the RJSClass's object named myObject.

• Methods support polymorphism.

Example: class myRJSClass methods <? myMethod { call java.lang.System.out.println "No parameters" } ; myMethod <@ java.lang.Integer num @> { call java.lang.System.out.println $num } ?> will create a RJSClass named myRJSClass with two methods named myMethod. create &myRJSClass myObject and call &myObject.myMethod prints the string "No parameters" in the system's console. create &myRJSClass myObject and call &myObject.myMethod 4 will print the integer 4 in the system's console.

LOOP:

Consider the following array for the examples listed below: java.lang.String[] myArray = { "String 1", "String 2", "String 3", "String 4", "String 5" } ;

• Used to iterate over a array.

Example: loop myArray<> { call java.lang.System.out.println myArray<#> } will iterate over the array named myArray from 0 to length of the array. The # represents the index of iteration. This will print String1, String2, String3, String4, String 5 in the system's console.

• Used to iterate over a given number range.

Example: loop myArray<1..3> { call java.lang.System.out.println myArray<#> } will iterate over the array named myArray from the index 1 to 3, which includes both indexes 1 and 3. The range is indicated using .. symbol. This will print String2, String 3, String 4 in the system's console.

• Can loop by stride.

Example: loop myArray<2> { call java.lang.System.out.println myArray<#> } will iterate over the array named myArray from index 0 to length of the array by taking a step of 2 to iterate over the array. This will print String 1, String 3, String 5 in the system's console.

• Reverse looping is also supported.

Example: loop myArray<3..0> { call java.lang.System.out.println myArray<#> } will iterate over the loop named myArray from index 3 to 0. This will print String 4, String 3, String 2, String 1 in the system's console.

• Ranged looping with stride is also supported.

Example: loop myArray<2..l, 2> { call java.lang.System.out.println myArray<#> } will iterate over the array named myArray from index 2 to length of the array which is represented by the letter l with stride 2. This will print String 3, String 5 in the sytem's console.

AS:

• Used to perform type casting.

Example: call java.lang.System.out.println (call (create java.util.Date date as java.lang.String).getClass) will cast the created java.util.Date object named date as java.lang.String object. Thus, class java.lang.String is printed in the system's console.

• Type cast will be performed only if type casting is valid as per Java standards.

Example: create java.util.Date date as java.lang.Integer is invalid.

• Casting to java.lang.String performs Object’s toString operation.

Example: call java.lang.System.out.println (create java.util.Date date 1479547474671 as java.lang.String) will cast the created java.util.Date object named date to java.lang.String and will print Sat Nov 19 14:54:34 IST 2016 in the system's console.

ARRAYS:

• Arrays can be created with RJS.

Example: create java.lang.Integer array=1:2:3:4:5 and loop &array<> { call java.lang.System.out.println &array<#> } will create an java.lang.Integer array with the values 1, 2, 3, 4, 5. The array values are to be separated by the symbol ***:***. This will print the integers 1, 2, 3, 4, 5 in the system's console.

• A particular index of an array can be accessed using the braces.

Example: call java.lang.System.out.println myArray<2> will print the value at index number 2 in the array object myArray.

VAR:

• Used to declare a variable or a function.

Example: var myVar = 5 will create a RJS variable named myVar with the value 5. var myFunction = { call java.lang.System.out.println "Hello World!" } will create a RJS function named myFunction which when called will print the string "Hello World" in the system console.

• Can declare an array of variables and functions.

Example: var myRJSArray = "Sanjeevi":10:{ compute 10+3 }

• RJS Functions supports polymorphism.

Example: var myRJSFunction = { call java.lang.System.out.println "Hello World" } , myRJSFunction = <@ java.lang.Integer num @> { call java.lang.System.out.println $num } creates two functions named myRJSFunction. The first method accepts no parameters whereas the second method accepts one integer parameter. call &myRJSFunction will print the string "Hello World" in the system console. call &myRJSFunction 3 will print the integer 3 in the system console.

• It is type independent.

Example: var myVariable=123 will initialize the variable named myVariable with the integer 123. assign (create java.util.Date date) to &myVariable and call java.lang.System.out.println &myVariable will create a new java.util.Date object named date and it is assigned to the RJS variable named myVariable. So the current date is printed in the system console.

• A var array can consist of both variables and functions.

Example: var myRJSArray = "Sanjeevi":10:{ compute 10+3 } is valid. But var myRJSArray = "Sanjeevi":10:{ call java.lang.System.out.println (compute 10+3) } is invalid because the function declared in the RJS array does not return a value. All RJS array functions should return a value.

• It is auto type casted to it’s assigned value’s type.

Example: var myVariable=123 and call java.lang.System.out.println (call &myVariable.getClass) will print class java.lang.Integer in the system console. var myVariable=123 and assign (create java.util.Date date) to &myVariable and call java.lang.System.out.println (call &myVariable.getClass) will print class java.util.Date in the system console.

INTERFACE:

• Objects for interfaces can be created through RJS. Interface object creation in RJS is similar to RJS Class declaration.

Example: create android.view.View$OnClickListener onClickListener <? onClick <@ android.view.View view @> { call java.lang.System.out.println "Hello World" } ?> will create an object for the interface android.view.View.OnClickListener. The method named onClick(android.view.View) for the interface android.view.View.OnClickListener is overridden with RJS code which would print the string "Hello World" on the system console whenever the click event happens for that view in this example.

• All abstract methods of an interface need not mandatorily be overrided while creating an object for the interface.

Example: create java.util.List list <? size { call java.lang.System.out.println 0 } ?> will create an object for the interface java.util.List but overrides only one method named size(). However, note that other method calls will fail except for the overridden methods for that interface as other methods have not been defined.