Parse Java code with JavaParser and find the statement type of parent nodes

Question

I have made a small program that uses JavaParser [1] to parse Java code and identify the types of statements that appear in the code. This has been implemented successfully. What I want to do next, and is a bit tricky, is to find the parent node for an if-statement, and check whether the first statement of the parent node is a while-loop. After confirming that the above statement is true, I also want to find if this if-statement is the last child of the parent node.

Following you can find an example of the above description:

void example() {
    int x = 1;
    int y = 1;
    while (y < 3) {
        while (x < 4) {
            x++;                
        }
        if (y < 5) {
            y++;  
        }
    }
    x = 0;
}

The main question I have with parsing the above code, is how to obtain that the parent node of if (y < 5 ) is a while-loop (while (y < 3)) and secondly, which might be even trickier, is how to identify that the if-statement of this example is the last statement before we skip back to the parent loop. There is also y++; inside the if but it might be skipped if the condition of the if is not true, so I do not want to consider it as the last child of the parent node. I believe what I should do is to check for the last "neighbour"? What I mean by neighbour is the relationship between the second while and the if of this example, i.e. they are at the same level.

My thoughts so far implemented:

//find if the if-statement has a parent node
if (currIf.getParentNode().isPresent()) {
    //find if the parent Node is a While loop
    Optional<Node> parent = currIf.getParentNode();
    parent.get().getBegin();
}

With the above code I am able to check if the if-statement has a parent node and I can find the location of the first while but I do not know how to confirm that it is a while statement and also implement the second described part.

UPDATE:

I managed to find how to check if the parent is a while-loop and currently trying to find a solution on how to identify that the if-statement is the last statement of its level (or hierarchy if you prefer).

Optional<WhileStmt> ifParent = currIf.findAncestor(WhileStmt.class);
//find if the if-statement has a parent node
if (ifParent.isPresent()) {
//find if the parent Node is a While loop
        Optional<Node> sameNode = ifParent.get().findFirst(Node.class, n -> n == currIf);
        if (sameNode.isPresent()) {
            System.out.println(sameNode);
        }
}

Lindstorm · Answer 1 · 2020-03-08T02:55:07.427

Your update could give you the wrong result if I am understanding it correctly. Yes, your solution will work if a WhileStmt is the parent, but it also could give you a WhileStmt a bit further up the tree.

Why can't you do something like the following?

 boolean parentIsWhileLoop = ifStmtNode.getParent() instanceof WhileStmt;

For determining if the ifStmt is the last node, you could do

 Node ifStmtParent = ifStmt.getParent();
 List<Node> ifStmtSibilings = ifStmtParent.getChildNodes();
 Node lastNode = ifStmtSiblings.get(ifStmtSiblings.size() - 1);
 boolean ifStmtIsLast = lastNode == ifStmt;

Parse Java code with JavaParser and find the statement type of parent nodes

1 Answers1