Java 字符串替换优先

Question

我正在阅读字符串

Is Mississippi a State where there are many systems.

我想用“t”或“T”替换每个单词中的第一个“s”或“S”（即保持相同的大小写）......这样输出是：

It Mitsissippi a Ttate where there are many tystems.

我试过了

s= s.replaceFirst("(?i)S", "t"); [which of course didn't work]

并尝试使用 string [] .split(Pattern.quote("\\s")) 然后试图弄清楚如何 replaceFirst() array 的每个元素，然后 return 将值返回到 string [但无法计算正确的做法]。

我认为\\G 可能有助于重新启动在下一个词，但没有得到任何地方。感谢您使用这 3 种方法的任何帮助。

Answer 1

我创建了一个方法 -

• 是通用的，
• 不使用replace 或split，并且
• 只使用一个循环。

以下是我的代码sn-p：

public static String replaceFirstOccurance(String sentence, char toChange, char changeWith) {
    StringBuilder temp = new StringBuilder();

    boolean changed = false;
    for (int i = 0; i < sentence.length(); i++) {
        if (!changed) {
            if (sentence.charAt(i) == toChange) {
                temp.append(changeWith);
                changed = true;
            } else if (sentence.charAt(i) == Character.toUpperCase(toChange)) {
                temp.append(Character.toUpperCase(changeWith));
                changed = true;
            } else {
                temp.append(sentence.charAt(i));
            }
        } else {
            if (sentence.charAt(i) == ' ') {
                changed = false;
            }
            temp.append(sentence.charAt(i));
        }
    }

    return temp.toString();
}

Answer 2

String ss = "Is Mississippi a State where there are many systems.";

String out = "";//replaced string
for (String s : ss.split(" ")) {
    int index = s.toUpperCase().indexOf('S');
    out += (s.replaceFirst("[s,S]", index!= -1 && s.charAt(index) == 'S' 
               ? "T" : "t")) + " ";
}

System.out.println(out);

Answer 3

使用以下对 Tim Biegeleisen 的答案的修正（在编辑他的帖子之前）

String input = "Is Mississippi a State where there are many systems.";
String[] parts = input.split(" ");
StringBuilder sb = new StringBuilder("");

for (String part : parts) {
    sb.append(part.replaceFirst("s", "t").replaceFirst("S", "T"));
    sb.append(" ");
}

System.out.println(sb.toString());

编辑 - 您可以使用 concat()

String input = "Is Mississippi a State where there are many systems.";
String[] parts = input.split(" ");

String output = "";

for (String part : parts) {
    output = output.concat(part.replaceFirst("s", "t").replaceFirst("S", "T") + " ");
}

    System.out.println(output);

更新

    String input = "Is Mississippi a State where there are many Systems.";
    String[] parts = input.split(" ");
    //StringBuilder sb = new StringBuilder("");

    String output = "";

    for (String part : parts) {
        output = output.concat(part.replaceFirst("s", "t") + " ");
    }

    String[] parts2 = output.split(" ");

    output = "";

    for (String part : parts2) {
        output = output.concat(part.replaceFirst("S", "T") + " ");
    }
    System.out.println(output);

Answer 4

还有一个不错的、紧凑的、基于流的解决方案：

String result = Stream.of(s.split(" "))
    .map(t -> t.replaceFirst("s", "t"))
    .map(t -> t.replaceFirst("S", "T"))
    .collect(Collectors.joining(" "));

Answer 5

Approach-1：不使用replace和split方法以获得更好的性能。

String str = "Is Mississippi a State where there are many systems.";
System.out.println(str);

char[] cArray = str.toCharArray();
boolean isFirstS = true;
for (int i = 0; i < cArray.length; i++) {
    if ((cArray[i] == 's' || cArray[i] == 'S') && isFirstS) {
        cArray[i] = (cArray[i] == 's' ? 't' : 'T');
        isFirstS = false;
    } else if (Character.isWhitespace(cArray[i])) {
        isFirstS = true;
    }
}
str = new String(cArray);

System.out.println(str);

编辑：方法 2：因为您需要使用 replaceFirst 方法，而您不想使用 StringBuilder，这里有一个适合您的选项：

String input = "Is Mississippi a State where there are many Systems.";
String[] parts = input.split(" ");
String output = "";

 for (int i = 0; i < parts.length; ++i) {
     int smallSIndx = parts[i].indexOf("s");
     int capSIndx = parts[i].indexOf("S");

     if (smallSIndx != -1 && (capSIndx == -1 || smallSIndx < capSIndx))
         output += parts[i].replaceFirst("s", "t") + " ";
     else
         output += parts[i].replaceFirst("S", "T") + " ";
 }

System.out.println(output); //It Mitsissippi a Ttate where there are many Tystems. 

注意：我更喜欢方法 1，因为它对于 replaceFisrt 和 @ 方法 没有开销 987654328@ , 字符串 append 或 concat

Answer 6

一种选择是将字符串拆分为单词，然后在每个单词上使用String.replaceFirst() 将s 的第一次出现替换为t（或您想要的任何其他字母）：

更新：

我重构了我的解决方案以找到任何s（大写或小写）的第一次出现，并对其应用适当的转换。

String input = "Is Mississippi a State where there are many systems.";
String[] parts = input.split(" ");
StringBuilder sb = new StringBuilder("");

for (int i=0; i < parts.length; ++i) {
    if (i > 0) {
        sb.append(" ");
    }
    int index = parts[i].toLowerCase().indexOf('s');
    if (index >= 0 && parts[i].charAt(index) == 's') {
        sb.append(parts[i].replaceFirst("s", "t"));
    }
    else {
        sb.append(parts[i].replaceFirst("S", "T"));
    }
}

System.out.println(sb.toString());

输出：

It Mitsissippi a Ttate where there are many tystems.

Answer 7

我的方法将较少依赖您提到的那些字符串方法。

String phrase;
String [] parts = phrase.split(" ");

for (int i = 0; i < parts.length; i++ ) {
    for (int j = 0; j < parts[i].length(); j++) {
        if (parts[i].charAt(j) == 's') {
            parts[i] = "t" + parts[i].substring(1);
            break;
        } else if (parts[i].charAt(0) == 'S') {
            parts[i] = "T" + parts[i].substring(1);
            break;
        }
    }
}

String modifiedPhrase = "";

for (int i = 0; i < parts.length; i++ ) {
    modifiedPhrase += parts[i] + " ";
}