IF to Hash refactoring

if2hash.java

//1) Starting code...
Color color;

if (branchLength == 10) { 

  color = PenColors.Greens.Lime;

} else if (branchLength == 20) {

  // ...

} else if (branchLength == 30) {

  // ...

}

//2) 1st Refactoring introduces the map, and replaces the first if statement.

// Add the map and the first case to the map

HashMap<Integer, Color> colors = new HashMap<Integer, Color>();

colors.put(10, PenColors.Greens.Lime);


Color color;



// rewrite the first branch to check the map

if (colors.containsKey(branchLength)) { 

  color = colors.get(branchLength);

} else if (branchLength == 20) {

  // ...

} else if (branchLength == 30) {

  // ...

}

//3) Refactorings 2 .. n replace the rest of the if branches.

// Add the map and the first case to the map

HashMap<Integer, Color> colors = new HashMap<Integer, Color>();

colors.put(10, PenColors.Greens.Lime);

colors.put(20, PenColors.Greens.ForestGreen);  // <-- 20 moved here


Color color;

if (colors.containsKey(branchLength)) { 

  color = colors.get(branchLength);

} else if (branchLength == 30) { // <--- 20 is gone, starts at 30 now

  // ...

}

//Finally only the first branch of the if statement remains, and you can remove the If, leaving behind only the map.