public class Test { public static void main(String[] args){ String s = "Samuel"+'B'; //String + char permitted, concatenation System.out.println(s.toUpperCase()); System.out.println('B'+"Samuel"); //char + String permitted, concatenation boolean vero = true; System.out.println("ZeroB"+vero); //String + boolean permitted, concatenation System.out.println(vero+"ZeroB"); //boolean + String permitted, concatenation int x = 9; System.out.println("Zero"+x); //String + int permitted, concatenation System.out.println(x+"Zero"); //int + String permitted, concatenation double c = 3.9; System.out.println("Zero"+c); //String + double permitted, concatenation System.out.println(c+"Zero"); //double + String permitted, concatenation System.out.println(x+c); //double + int and int + double permitted, double sum System.out.println('c'+x); //char + int permitted, sum of int System.out.println(x+'c'); //int + char permitted, sum of int System.out.println('c'+c); //char + double permitted, sum of double System.out.println(c+'c'); //double + char permitted, sum of double //System.out.println('c'+vero); char + boolean not legal //System.out.println(vero+'c'); boolean + char not legal //System.out.println(vero+c); boolean + double not legal //System.out.println(vero+x); boolean + int not legal //System.out.println(c+vero); int/double + bool not legal char t = 'b'; //t = t + 1; Incompatible types. Found: 'int', required: 'char' System.out.println(""+5);// 5 int[] histogram = letterHist("alpha"); for(int occurrence: histogram){ System.out.println(occurrence); } } public static int[] letterHist(String s){ String lows = s.toLowerCase(); int[] histogram = new int[26]; for(int i=0; i < lows.length(); i++){ if((int)lows.charAt(i)-97<26&&(int)lows.charAt(i)-97>=0) histogram[(int)lows.charAt(i)-97]++; } return histogram; } }