Assembler: Modifying fields and methods

How do you access the assembler?

When you right click a field or method definition in Recaf selecting "Edit with assembler" will open the assembler window. Fields and methods both use the same assembler system, but each use a different syntax for defining field or method specific properties.

Method Assembler

The method assembler lets you edit methods as text.



Given the following Java code, lets take a look at the assembler

public double accept(String expression) {
    String matched = MatchUtil.match("^[-]?[0-9.]+[+-][-]?[0-9.]+", expression);
    String op = MatchUtil.findFirst(matched, "+", "-");
    int index = matched.indexOf(op);
    String left = matched.substring(0, index);
    String right = matched.substring(index + 1, matched.length());
    expression = expression.replace(matched, String.valueOf(switch (op) {
        case "+" -> this.evaluate(left) + this.evaluate(right);
        case "-" -> this.evaluate(left) - this.evaluate(right);
        default -> throw new IllegalStateException();
    return this.evaluate(expression);


The screenshot on the left shows the Analysis tab of the assembler window. This tab is shows information about the current line you have your cursor on. In the picture I have selected a line to make it more visible. There are two columns...

The left column shows the value of variables at the given point. For primitive types and strings the exact value is simulated when possible.

The right column shows the stack at the given point. The most recent items of the stack appear on the bottom of the list. In this case we can see that three strings are on the stack. The top of the stack contains - and just below it is +. Below that is an unknown string, loaded from the matched variable.


The screenshot on the right shows a table displaying the current local variables. Unlike the analysis tab this does not show the value in the variable, just information about the variable.

You can immediately jump to any instruction that references a variable by right clicking on it in the table. This brings up the referrer menu.

See also:

Field Assembler

The field assembler lets you edit fields as text.