String line = ...;
StringBuilder sb = new StringBuilder();
for(int i = 0; i < line.length(); i++) {
switch(line.charAt(i)) {
case 031 : sb.append('*'); break;
case 035 : sb.append('+'); break;
case 037 : sb.append(':'); break;
case 034 : sb.append('\''); break;
default : sb.append(line.charAt(i));
}
}
line = sb.toString();