I want something in my code that will generate loops and its corresponding body dynamically. My code right now looks like this for which I have explicitly defined each loop and loop body, each of which runs based on a variable "len"'s value. How can I change it so that the loop codes such as those that I have written for each condition are generated dynamically?
ArrayList<String> mapAll(String input){
int len = input.length();
ArrayList<String> outputs= new ArrayList<>();
//String[] outputs = new String[len];
ArrayList<String> outputStrings= new ArrayList<>();
for (int i = 0; i <len ; i++)
outputs.add(mapOne(Character.toString(input.charAt(i))));
if (len == 1)
for (int i = 0; i <outputs.get(len -1).length() ; i++)
outputStrings = outputs;
else if (len == 2)
for (int i = 0; i <outputs.get(len-2).length() ; i++)
for (int j = 0; j < outputs.get(len - 1).length(); j++)
outputStrings.add(Character.toString(outputs.get(len - 2).charAt(i)) + outputs.get(len - 1).charAt(j));
else if(len == 3)
for (int i = 0; i <outputs.get(len-3).length(); i++)
for (int j = 0; j <outputs.get(len-2).length(); j++)
for (int k = 0; k <outputs.get(len-1).length(); k++)
outputStrings.add(Character.toString(outputs.get(len-3).charAt(i)) + outputs.get(len - 2).charAt(j) + outputs.get(len - 1).charAt(k));
else if(len==4)
for (int i = 0; i < outputs.get(len-4).length(); i++)
for(int j = 0; j < outputs.get(len-3).length(); j++)
for(int k = 0; k < outputs.get(len-2).length(); k++)
for(int l = 0; l < outputs.get(len-1).length(); l++)
outputStrings.add(Character.toString(outputs.get(len-4).charAt(i)) + outputs.get(len-3).charAt(j) + outputs.get(len-2).charAt(k)+ outputs.get(len-1).charAt(l));
return outputStrings;
}
Implementation of mapOne method:
private String mapOne(String in){
String out;
switch (in){
case "a":
out = "a"+"q"+"w"+"s"+"z";
break;
case "b":
out = "b"+"g"+"h"+"v"+"n"+" ";
break;
case "c":
out = "c"+"d"+"f"+"x"+"v"+" ";
break;
case "d":
out = "d"+"e"+"r"+"s"+"f"+"x"+"c";
break;
case "e":
out = "e"+"w"+"r"+"s"+"d";
break;
case "f":
out = "f"+"r"+"t"+"d"+"g"+"c"+"v";
break;
case "g":
out = "g"+"t"+"y"+"f"+"h"+"v"+"b";
break;
case "h":
out = "h"+"y"+"u"+"g"+"j"+"b"+"n";
break;
case "i":
out = "i"+"u"+"o"+"j"+"k";
break;
case "j":
out = "j"+"u"+"i"+"h"+"k"+"n"+"m";
break;
case "k":
out = "k"+"i"+"o"+"j"+"l"+"m";
break;
case "l":
out = "l"+"o"+"p"+"k";
break;
case "m":
out = "m"+"j"+"k"+"n"+" ";
break;
case "n":
out = "n"+"h"+"j"+"b"+"m"+" ";
break;
case "o":
out = "o"+"i"+"p"+"k"+"l";
break;
case "p":
out = "p"+"o"+"l";
break;
case "q":
out = "q"+"w"+"a";
break;
case "r":
out = "r"+"e"+"t"+"d"+"f";
break;
case "s":
out = "s"+"w"+"e"+"a"+"d"+"z"+"x";
break;
case "t":
out = "t"+"r"+"y"+"f"+"g";
break;
case "u":
out = "u"+"y"+"i"+"h"+"j";
break;
case "v":
out = "v"+"f"+"g"+"c"+"b"+" ";
break;
case "w":
out = "w"+"q"+"e"+"a"+"s";
break;
case "x":
out = "x"+"s"+"d"+"z"+"c"+" ";
break;
case "y":
out = "y"+"t"+"u"+"g"+"h";
break;
case "z":
out = "z"+"a"+"s"+"x";
break;
case " ":
out = " "+"x"+"c"+"v"+"b"+"n"+"m";
break;
default:
out = "#";
}
return out;
}
Clean version with streams:
static ArrayList<String> mapAll1(String input) {
int len = input.length();
ArrayList<String> outputs = new ArrayList<>();
//String[] outputs = new String[len];
ArrayList<String> outputStrings = new ArrayList<>();
for (int i = 0; i < len; i++)
outputs.add(mapOne(Character.toString(input.charAt(i))));
if (len == 1)
for (int i = 0; i < outputs.get(len - 1).length(); i++)
outputStrings = outputs;
else {
outputStrings = IntStream
.range(0, len)
// get last n strings from outputs, starts from last
.mapToObj(i -> outputs.get(len - (i + 1)))
// transform List<String> into List<List<String>>,
.map(x -> new ArrayList<>(x.chars()
.mapToObj(Character::toString)
.collect(Collectors.toList()))
)
// reduce
.reduce(new ArrayList<>(), (acc, list) -> new ArrayList<>(
acc.isEmpty() ? list : list.stream()
.flatMap(prefix -> acc.stream()
.map(tail -> prefix + tail)
).collect(Collectors.toList())));
}
return outputStrings;
}
The main part written in old way with further explanation
if (len == 1)
for (int i = 0; i < outputs.get(len - 1).length(); i++)
outputStrings = outputs;
else {
ArrayList<ArrayList<String>> tokenizeStrings = new ArrayList();
// get last n strings from outputs, starts from last
for (int i = 0; i < len; i++) {
// transform List<String> into List<List<String>>,
tokenizeStrings.add( new ArrayList<>(outputs.get(len - (i + 1)).chars()
.mapToObj(Character::toString)
.collect(Collectors.toList())));
}
outputStrings = new ArrayList<>();
// reduce
for (ArrayList<String> list: tokenizeStrings) {
if (outputStrings.isEmpty()) {
// first iteration just makes a copy
outputStrings = list;
} else {
ArrayList<String> temp = new ArrayList<>();
for (String prefix : list) {
// for the rest iterations use string 'prefix' from current list
// and add it in front of every string from main list 'outputStrings'
for (String tail : outputStrings) {
temp.add(prefix + tail);
}
}
// replace outputStrings with temp list
outputStrings = temp;
}
}
}
return outputStrings;