java 字符串操作

Question

好的，所以我尝试在您的帮助下学习更多有关 Java 中的字符串和链接字符串的知识。

现在我知道字符串是不可变的，但我很难做到这一点，例如:

Implement the method

public static String notReplace(String str)

The method takes a String as its input and returns a String in which every occurrence of the lowercase word "is" has been replaced with "is not". The word "is" should not 2 be immediately preceded or followed by a letter -- so for example the "is" in "this" should not be replaced. (Note: Character.isLetter(char) tests if a char is a letter.)

示例:
notReplace("是测试") → "不是测试"
notReplace("is-iswise") → "is not-isnotwise"

这是我写的:

public class NotReplace{

    public static void main(final String[] args){
        final String str2 = "is no";
        System.out.println(notReplace(str2));

    }

    public static String notReplace(final String str){
        final int times = str.length();

        final StringBuilder sb = new StringBuilder(str);
        for(int i = 0; i <= times; i++){
            if((str.charAt(i) == 'i') && (str.charAt(i + 1) == 's')
                && !Character.isLetter(str.charAt(i + 2))){
                sb.insert(i, "not");

            }
            final String str1 = sb.toString();
            return str1;

        }
    }
}

我相信这完全是一团糟，我很乐意了解更多如何在这种情况下使用字符串。

谢谢

编辑:我无法使用replaceAll函数。

Answer 1

您可能会发现这很有趣

String text = "This is a test. It is"; // note the 'is' at the end.
String text2 = text.replaceAll("\\bis\\b", "is not");
System.out.println(text +" => "+text2);

打印

This is a test. It is => This is not a test. It is not

下面的方法可以实现这一点

 public static String notReplace(final String str){
    final StringBuilder sb = new StringBuilder()
                                 .append(' ').append(str).append(" ");
    for (int i = 0; i < sb.length() - 2; i++) {
        if (!Character.isLetter(sb.charAt(i)) &&
                sb.charAt(i + 1) == 'i' &&
                sb.charAt(i + 2) == 's' &&
                !Character.isLetter(sb.charAt(i + 3))) {
            sb.insert(i + 3, " not");
            i += 5;
        }
    }
    return sb.substring(1, sb.length() - 1);
}

在开头和结尾添加空格以避免边界检查。