Java從數組中打印某些字符

Question

我有一個字符串數組，如下所示：

[67, +, 12, -, 45]

我想打印出來，看起來像這樣：

67 12 + 45 -

這是我試圖用來做這個的代碼。

String[] temp = line.split(" ");
            String tmp = line.replaceAll("\\s+","");

            for(int i = 0; i < temp.length; i++)
            {
                if(isInt(temp[i]) == false)
                {
                    expression = temp[i];
                    firstExp = true;
                }
                else if(isInt(temp[i]) == false && firstExp == true && secondExp == false)
                {
                    System.out.print(expression);
                    secondExp = true;
                }
                else if(isInt(temp[i]) == false && firstExp == true && secondExp == true)
                {
                    System.out.print(expression);
                    firstExp = false;
                    secondExp = false;
                }
                else
                {
                    System.out.print(temp[i]);
                }
            }

firstExp和secondExp是布爾值，用於檢查應該出現在數組中的表達式。 isInt（）只是一種用於確定字符串是否為數字的方法。 現在，所有這些代碼都輸出：

671245

Answer 1

public static void main (String[] args) throws java.lang.Exception
    {
        String[] expr = new String[]{"67", "+", "45", "-", "12", "*", "5", "/", "78"};
        int current = 0;
        StringBuilder postfix = new StringBuilder();

        // handle first three
        postfix.append(expr[current]).append(" ");
        postfix.append(expr[current+2]).append(" ");
        postfix.append(expr[current+1]).append(" ");
        current += 3;

        // handle rest
        while( current <= expr.length-2 ){
            postfix.append(expr[current+1]).append(" ");
            postfix.append(expr[current]).append(" ");
            current += 2;
        }

        System.out.println(postfix.toString());
    }

輸出：

67 45 + 12 - 5 * 78 /

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Answer 2

我想你要做的是將中綴表達式轉換為post fix。 一段時間后我寫了以下代碼：

    public class InfixToPostfix {
   private Stack stack;
   private String input;
   private String output = "";
   public InfixToPostfix(String in) {
      input = in;
      int stackSize = input.length();
      stack = new Stack(stackSize);
   }
   public String translate() {
      for (int j = 0; j < input.length(); j++) {
         char ch = input.charAt(j);
         switch (ch) {
            case '+': 
            case '-':
            hastOperator(ch, 1); 
            break; 
            case '*': 
            case '/':
            hastOperator(ch, 2); 
            break; 
            case '(': 
            stack.push(ch);
            break;
            case ')': 
            hasSuperior(ch); 
            break;
            default: 
            output = output + ch; 
            break;
         }
      }
      while (!stack.isEmpty()) {
         output = output + stack.pop();
      }
      System.out.println(output);
      return output; 
   }
   public void hastOperator(char op, int precedence) {
      while (!stack.isEmpty()) {
         char opTop = stack.pop();
         if (opTop == '(') {
            stack.push(opTop);
            break;
         }
         else {
            int prec2;
            if (opTop == '+' || opTop == '-')
            prec2 = 1;
            else
            prec2 = 2;
            if (prec2 < precedence) { 
               stack.push(opTop);
               break;
            }
            else
            output = output + opTop;
         }
      }
      stack.push(op);
   }
   public void hasSuperior(char ch){ 
      while (!stack.isEmpty()) {
         char chx = stack.pop();
         if (chx == '(') 
         break; 
         else
         output = output + chx; 
      }
   }
   public static void main(String[] args) 
   throws IOException {
      String input = "67 + 12 - 45";
      String output;
      InfixToPostfix theTrans = new InfixToPostfix(input);
      output = theTrans.translate(); 
      System.out.println("Postfix is " + output + '\n');
   }
   class Stack {
      private int maxSize;
      private char[] stackArray;
      private int top;
      public Stack(int max) {
         maxSize = max;
         stackArray = new char[maxSize];
         top = -1;
      }
      public void push(char j) {
         stackArray[++top] = j;
      }
      public char pop() {
         return stackArray[top--];
      }
      public char peek() {
         return stackArray[top];
      }
      public boolean isEmpty() {
         return (top == -1);
     }
    }
    }

您可能需要修改此程序以從數組中讀取，但這非常簡單。

Answer 3

以下是您如何在一行中完成的：

System.out.println(Arrays.toString(temp).replaceAll("[^\\d +*/-]", "").replaceAll("[+*/-]) (\\d+)", "$2 $1"));