Java - Switch Statement not functioning properly, System.out.println's mysteriously repeating -

seems basic problem, google nor have helped me resolve issue. made program out of sheer boredom allows user input string of text, , edit colour of said text using colour codes game minecraft. added advanced function allows user colourize each individual letter in given string - problems arise. @ end of advanced part of program, prompt user menu asks them want - return main part of program, restart advanced section, or exit program altogether. both options 1 , 3 work expected, when try restart advanced portion of program, strangely repeats menu on , on until select option. have rewritten how user's choice evaluated numerous times, rewrote plenty other sections of program, hoping logical error, no avail. here menu they're shown:

    system.out.println("\n======= devtest terminated=======\n");     system.out.println("what do?");     system.out.println("1: return main program");     system.out.println("2: run devtest again");     system.out.println("3: exit program");      int useroption = input.nextint();      switch(useroption){         case 1:             system.out.println();             start.main(null);             break;         case 2:             devtests.rainbowtest();             break;         case 3:              system.exit(0);         default:             system.exit(0);             break;     } 

when user enters "2" , hits enter, program runs first line of advanced program (prompting user enter string), instantly runs menu again. i've been looking on few hours now, , have yet come solutions. i've added entire advanced program @ end of post, guys can see that's going on, , before ask, no, primary part of program isn't interfering way.

any suggestions/comments appreciated.

note: realize of code isn't complete - please realize still in-progress, , until issue resolved, quite time. :p

import java.util.scanner;  public class devtests {  static scanner input = new scanner(system.in);  public static void rainbowtest(){      system.out.println();     system.out.println("enter string:");     string userstring = input.nextline();      int stringlength = userstring.length();      system.out.println();      string rainbowstring = "";      for(int = 1; <= stringlength; i++){         system.out.println("enter colour #" + + ":");         system.out.println("black");         system.out.println("white");         system.out.println("blue");         system.out.println("dark blue");         system.out.println("green");         system.out.println("dark green");         system.out.println("aqua");         system.out.println("dark aqua");         system.out.println("red");         system.out.println("dark red");         system.out.println("purple");         system.out.println("dark purple");         system.out.println("gray");         system.out.println("dark gray");         system.out.println("yellow");         system.out.println("gold");         string usercolour2 = input.nextline();         system.out.println();          switch (usercolour2){         case "black":             usercolour2 = "§0";             break;         case "white":             usercolour2 = "§f";             break;         case "blue":             usercolour2 = "§9";             break;         case "dark blue":             usercolour2 = "§1";             break;         case "green":             usercolour2 = "§a";             break;         case "dark green":             usercolour2 = "§2";             break;         case "aqua":             usercolour2 = "§b";             break;         case "dark aqua":             usercolour2 = "§3";             break;         case "red":             usercolour2 = "§c";             break;         case "dark red":             usercolour2 = "§4";             break;         case "purple":             usercolour2 = "§d";             break;         case "dark purple":             usercolour2 = "§5";             break;         case "gray":             usercolour2 = "§7";             break;         case "dark gray":             usercolour2 = "§8";             break;         case "yellow":             usercolour2 = "§e";             break;         case "gold":             usercolour2 = "§6";             break;         default:             system.out.println("please select colour. \n");             break;         }          rainbowstring += usercolour2 + userstring.charat(i - 1);     }      system.out.println(rainbowstring);      system.out.println("\n======= devtest terminated=======\n");     system.out.println("what do?");     system.out.println("1: return main program");     system.out.println("2: run devtest again");     system.out.println("3: exit program");      int useroption = input.nextint();      switch(useroption){         case 1:             system.out.println();             start.main(null);             break;         case 2:             devtests.rainbowtest();             break;         case 3:              system.exit(0);         default:             system.exit(0);             break;         }     } } 

when using int useroption = input.nextint() not read end-of-line symbol, it's being read next string userstring = input.nextline() call. result empty userstring, skip for loop , go again last menu. fix use:

int useroption = input.nextint(); input.nextline();