Java String ReplaceFirst

Question

我正在读一个字符串

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”（即保持相同的情况）......以便输出为：

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a来分割字符串 字符串[] .split(Pattern.quote("\\s"))然后尝试找出如何replaceFirst() array的每个元素，然后将值返回到string [ 但无法找到正确的方法]。

我认为\\G可能有助于重新启动下一个字，但却没有。任何使用这3种方法的帮助都表示赞赏。

Answer 1

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） ：

<强>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());

<强>输出：

It Mitsissippi a Ttate where there are many tystems.

Answer 2

方法-1：不使用replace和split方法以获得更好的效果。

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：由于您需要使用replaceFirst方法，而您不想使用StringBuilder，这里有一个选项：

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 ，因为方法replaceFisrt的无开销和split，字符串append或concat

Answer 3

使用以下修正Tim Biegeleisen的答案（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);

<强>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

我创建了一种方法 -

• 是通用的，
• 不使用WaveShortMessage* wsm = prepareWSM("data", dataLengthBits, channel, dataPriority, -1,2); wsm->setWsmData(blockedRoadId.c_str()); int byteLen = blockedRoadId.length(); // assuming that one char = one byte wsm->addByteLength(byteLen); 或replace和
• 仅使用一个循环。

以下是我的代码段：

split

Answer 5

我的方法将更少依赖于您提到的字符串方法。

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] + " ";
}

Answer 6

还有一个很好的，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 7

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);