Detect shared statements in branches

[Luro02]

What it does

Detects common statements at the start or end of conditional branches like if/else and suggests moving them before the if branch or after it.

To what can this be applied?

• if/else branches
• switches
• (methods?)

Some things to be careful of:

• the condition should not be used in the statements (for example below it should only move the statement if it does not access this.first)
• conditions might have side-effects
• else ifs might be difficult to work with / hard to give sensible feedback to the student -> I would suggest ignoring it

Lint Name

DUPLICATE_CODE

Category

general

Advantage

No response

Drawbacks

No response

Example

if (this.first == null) {
    ListCell newListCell = new ListCell(new int[this.arraySize], this.last, null);
    this.first = newListCell;
    this.last = newListCell;
    this.numberOfCells++;
    // returns always true here, because adding to a new array isn´t problematic
    // (array size > 0)
    return newListCell.addElement(element);
} else {
    ListCell newListCell = new ListCell(new int[this.arraySize], this.last, null);
    this.last.next = newListCell;
    this.last = newListCell;
    this.numberOfCells++;
    return newListCell.addElement(element);
    // returns always true here, because adding to a new array isn´t problematic
    // (array size > 0)
}

Could be written as:

ListCell newListCell = new ListCell(new int[this.arraySize], this.last, null);

if (this.first == null) {
    this.first = newListCell;
} else {
    this.last.next = newListCell;
}

this.last = newListCell;
this.numberOfCells++;
return newListCell.addElement(element);