GenerateSignatures.java

public class GenerateSignatures {

    public static void main(String... args) {
        Parameter[] values = new Parameter[]{new Parameter("A", "int"), new Parameter("B", "String"), new Parameter("C", "long")};

        Parameter[][] result = multiply(values);

        for (int i = 0; i < result.length; i++) {
            for (int k = 0; k < result[i].length; k++) {
                System.out.print(result[i][k].toString() + " ");
            }
            System.out.println("");
        }
    }

    public static Parameter[][] multiply(Parameter[] params) {
        Parameter[][] result = new Parameter[1][params.length];

        for (int i = 0; i < params.length; i++) {
            result[0][i] = new Parameter(params[i].name);
        }

        for (Parameter param : params) {
            result = multiply(result, param, params.length);
        }

        return result;
    }

    private static Parameter[][] multiply(Parameter[][] generate, Parameter placeholder, int length) {
        String[] types = new String[]{"MyCustomType", placeholder.type};

        Parameter[][] results = new Parameter[types.length * generate.length][length];
        int n = 0;
        for (int i = 0; i < types.length; i++) {
            for (int j = 0; j < generate.length; j++) {
                for (int k = 0; k < length; k++) {
                    results[n][k] = replace(generate[j][k], placeholder, types[i]);
                }
                n++;
            }
        }
        return results;
    }

    private static Parameter replace(Parameter result, Parameter placeholder, String type) {
        if (!placeholder.name.equals(result.name)) {
            return new Parameter(result);
        }

        if (result.hasType()) {
            return new Parameter(result);
        } else {
            return new Parameter(result.name, type);
        }
    }

    public static class Parameter {

        private final String name;
        private final String type;

        public Parameter(String name) {
            this.name = name;
            this.type = null;
        }

        public Parameter(String name, String type) {
            this.name = name;
            this.type = type;
        }

        public Parameter(Parameter base) {
            this(base.name, base.type);
        }

        public boolean hasType() {
            return this.type != null;
        }

        @Override
        public String toString() {
            return type + " " + name;
        }
    }

}