java - Javaで文字列式から部分式を抽出する方法は?

Question

文字列式を仮定すると、(x1(x2)(x3)(x4(x5(x6)(x7)))(x8))特定の深さの部分文字列 (つまり、部分式) を抽出する方法は?

検索項目が x4 の場合、部分式は(x4(x5(x6)(x7)))、 検索項目が x5 の場合、部分式は(x5(x6)(x7))

Answer 1

    String source = "(x1(x2)(x3)(x4(x5(x6)(x7)))(x8))";
    String searchCriteria = "x4";

    // searching in the String assuming it is Mathematical expressions

    int searchCriteriaCount = searchCriteria.length();
    int firstMatchedCharIndex = 0;
    int lastMatchedCharIndex = 0;

    knowingIndex:
    for(int i = 0;i < source.length();i++){
        String currentSequence = source.substring(i, i+searchCriteriaCount);
        if(currentSequence.equals(searchCriteria)){
            firstMatchedCharIndex = i;
            break knowingIndex;
        }
    }

    char openingBracket = '(';
    char closingBracket = ')';
    int openingBracketsCount = 0;
    int closingBracketsCount = 0;

    char[] sourceChars = source.toCharArray();

    fullCriteria:
    for(int i = firstMatchedCharIndex-1;i<sourceChars.length;i++){
        if(sourceChars[i] == openingBracket){
            openingBracketsCount++;
        }

        if(sourceChars[i] == closingBracket){
            closingBracketsCount++;
        }

        if(openingBracketsCount == closingBracketsCount){
            lastMatchedCharIndex = i;
            break fullCriteria;
        }

    }

    String finalEquation = source.substring(firstMatchedCharIndex-1, lastMatchedCharIndex+1);

    System.out.println(finalEquation);