我正在尝试学习Java中的哈希映射和2D数组。我们有一个任务，因为有一个扫描仪接受一个字符串并将其转换为莫尔斯电码。我们使用的代码基于一个充满if语句的方法，但我想学习如何使用list，hashmaps或2D数组做这样的事情。我的代码如下：
import java.util.*;
public class MorseConversion
{
public static void main(String[] args)
{
Scanner userInput = new Scanner(System.in);
System.out.println("Please enter a phrase to convert to morse code: ");
String userString = userInput.nextLine();
System.out.println("");
System.out.println(stringConvert(userString));
}
public static String stringConvert(String userString)
{
String currentChar;
String getMorseChar;
String convertedString = "";
for (int i = 0; i < userString.length(); i++)
{
//Get character at i position
currentChar = userString.charAt(i) + "";
//convert character to morse code
getMorseChar = convert(currentChar);
//seperate words with the | symbol
if (getMorseChar.equals(" "))
{
convertedString = convertedString + " | ";
}
else
{
//concat the converted letter
convertedString = convertedString + getMorseChar;
//Add a space between each letter
if (!getMorseChar.equals(" "))
{
convertedString = convertedString + " ";
}
}
}
return convertedString;
}
public static String convert (String toEncode)
{
String morse = toEncode;
if (toEncode.equalsIgnoreCase("a"))
morse = ".-";
if (toEncode.equalsIgnoreCase("b"))
morse = "-...";
if (toEncode.equalsIgnoreCase("c"))
morse = "-.-.";
if (toEncode.equalsIgnoreCase("d"))
morse = "-..";
if (toEncode.equalsIgnoreCase("e"))
morse = ".";
if (toEncode.equalsIgnoreCase("f"))
morse = "..-.";
if (toEncode.equalsIgnoreCase("g"))
morse = "--.";
if (toEncode.equalsIgnoreCase("h"))
morse = "....";
if (toEncode.equalsIgnoreCase("i"))
morse = "..";
if (toEncode.equalsIgnoreCase("j"))
morse = ".---";
if (toEncode.equalsIgnoreCase("k"))
morse = "-.-";
if (toEncode.equalsIgnoreCase("l"))
morse = ".-..";
if (toEncode.equalsIgnoreCase("m"))
morse = "--";
if (toEncode.equalsIgnoreCase("n"))
morse = "-.";
if (toEncode.equalsIgnoreCase("o"))
morse = "---";
if (toEncode.equalsIgnoreCase("p"))
morse = ".--.";
if (toEncode.equalsIgnoreCase("q"))
morse = "--.-";
if (toEncode.equalsIgnoreCase("r"))
morse = ".-.";
if (toEncode.equalsIgnoreCase("s"))
morse = "...";
if (toEncode.equalsIgnoreCase("t"))
morse = "-";
if (toEncode.equalsIgnoreCase("u"))
morse = "..-";
if (toEncode.equalsIgnoreCase("v"))
morse = "...-";
if (toEncode.equalsIgnoreCase("w"))
morse = ".--";
if (toEncode.equalsIgnoreCase("x"))
morse = "-..-";
if (toEncode.equalsIgnoreCase("y"))
morse = "-.--";
if (toEncode.equalsIgnoreCase("z"))
morse = "--..";
if (toEncode.equalsIgnoreCase("0"))
morse = "-----";
if (toEncode.equalsIgnoreCase("1"))
morse = ".----";
if (toEncode.equalsIgnoreCase("2"))
morse = "..---";
if (toEncode.equalsIgnoreCase("3"))
morse = "...--";
if (toEncode.equalsIgnoreCase("4"))
morse = "....-";
if (toEncode.equalsIgnoreCase("5"))
morse = ".....";
if (toEncode.equalsIgnoreCase("6"))
morse = "-....";
if (toEncode.equalsIgnoreCase("7"))
morse = "--...";
if (toEncode.equalsIgnoreCase("8"))
morse = "---..";
if (toEncode.equalsIgnoreCase("9"))
morse = "----.";
if (toEncode.equalsIgnoreCase("."))
morse = ".-.-";
if (toEncode.equalsIgnoreCase(","))
morse = "--..--";
if (toEncode.equalsIgnoreCase("?"))
morse = "..--..";
return morse;
}
}
我出于好奇而严格地这样做。我已经把它砸到了我的脑海里，像这样的冗余是一个巨大的禁忌。提前谢谢！
答案 0 :(得分：5)
更简单的方法是使用初始化程序将字符作为键加载到哈希映射中。然后，在循环输入字符串中的字符时，只需执行
即可在课程开始时做这样的事情：
private static HashMap<String, String> codes = new HashMap<String, String>();
static{
codes.put("a", ".-");
codes.put("b", "-...");
bla bla bla
}
然后在你的循环中
//convert character to morse code
getMorseChar = convert(currentChar);
你会有
getMorseChar = code.get(currentChar.toLowerCase());
没有更讨厌的elseif声明。
答案 1 :(得分：0)
以下是对2-D阵列有清晰理解的优化代码
public class MorseCode {
public static Scanner sc;
public static void main(String args[]) throws IOException //Input Output Exception is added to cover the BufferedReader
{
int option = 0;
String sentence = "",answer = "",answer1 = "";
char[] english = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
'y', 'z', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0',
',', '.', '?' }; //Defining a Character Array of the English Letters numbers and Symbols so that we can compare and convert later
String[] morse = { ".-", "-...", "-.-.", "-..", ".", "..-.", "--.", "....", "..",
".---", "-.-", ".-..", "--", "-.", "---", ".---.", "--.-", ".-.",
"...", "-", "..-", "...-", ".--", "-..-", "-.--", "--..", ".----",
"..---", "...--", "....-", ".....", "-....", "--...", "---..", "----.",
"-----", "--..--", ".-.-.-", "..--.." }; //Defining an Array of String to hold the Morse Code value of Every English Letter,Number and Symbol in the same order as that of the character Array
sc = new Scanner(System.in);
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println(">>>>Welcome to MorseCode Software<<<<");
System.out.println("");
do
{
System.out.println("-->Enter the Option Corresponding to the Task you want to Perform ");
System.out.println("->1.Generate Morse Code<- OR ->2.Generate English Language<- OR ->3.Exit ");
System.out.print("->");
while(!sc.hasNextInt()) //Repeat Until the next Item is an Integer i.e Until the Next Item is an Integer Keep on Repeating it
{//NOTE- The hasnext() function is also used when we are using the Iterator where the next input is always checked and then if it is valid it is allowed to be entered
System.out.println("");
System.err.println("-->ERROR<-->Enter Digits Only<--");
System.out.print("->");
sc.next(); //Repeat and Discard the previous Inputs which are not valid
}
option = sc.nextInt();
switch(option)
{
case 1:
{
System.out.println("");
System.out.println("-->Enter the Sentence that you want to Transmit Using the Morse Code ");
System.out.print("->");
sentence = br.readLine();
System.out.println("");
sentence = sentence.toLowerCase(); //Because morse code is defined only for the lower case letters and the numbers and the Symbols will remain the Same
char[] morsec = sentence.toCharArray();
for(int i = 0; i < morsec.length;i++) //The loop will run till i is less than the number of characters in the Sentence because Every Character needs to Be Converted into the Respective Morse Code
{//For Every Letter in the User Input Sentence
for(int j = 0;j<english.length;j++) //For Every Character in the morsec array we will have to traverse the entire English Array and find the match so that it can be represented
{
if(english[j] == morsec[i]) //If the Character Present in English array is equal to the character present in the Morsec array then Only Execute
{//Always remember that the condition in the Inner loop will be the first to be Equated in the If Statement because that will change until the characters match
answer = answer + morse[j] + " "; //After Every Letter is generated in the Morse Code we will give a Space
} //Since the Letters in the English char and the symbols present in the morse array are at the Same Index
}
}
System.out.println("-->The Morse Code Translation is:- ");
System.out.print(">> ");
System.out.println(answer);
System.out.println("");
break;
}
case 2:
{
System.out.println("");
System.out.println("-->Enter the Morse Code and After Every Letter add Space in Between ");
System.out.print("-> ");
sentence = br.readLine();
System.out.println("");
String[] morsec = sentence.split(" "); //To use the split function to Convert Every Morse Code String as a Separate Entry in the STring array
for(int i = 0;i < morsec.length;i++)
{//For Every morse code Letter Entered
//Remember - We are Splitting on the Basis of the space
for(int j = 0;j < morse.length;j++)
{
if(morse[j].equals(morsec[i])) //When you are comparing the String you have to Do this and not ==
{
answer1 = answer1 + english[j]; //Since the characters in the Morse array and the English Array are in the Same Index
}
}
}
System.out.println("-->The English Language Translation is:- ");
System.out.print(">> ");
System.out.println(answer1);
System.out.println("");
break;
}
case 3:
{
System.out.println("");
System.out.println(">>Thank you For Using this Service<<");
System.out.println("");
break;
}
default:
{
System.err.println("-->ERROR<-->Invalid Option Entered<--");
System.out.println("");
break;
}
}
}
while(option!=3);
}
}
希望代码没有混淆