Question

我试图使用indexOf查找所有出现的字符＆＃39;＆＃39;在一个句子里。例如，如果句子是＆＃34;有一天我去那里＆＃34;，它应该返回3.

我能够做到这一点直到它找到第一个索引，但我不确定如何编写循环。我最初有一个搜索整个字符串的for循环，但它返回的是完整的字符串字符长度，而不是我指定字符的出现次数。如何编写一个可以找到所有单词出现的循环？谢谢。

import java.util.Scanner;

public class TheFinder
{
    public static void main (String[] args)
    {
        String theString = "";
        Scanner enter = new Scanner(System.in);

        System.out.println("Please enter a sentence: ");
        theString = enter.nextLine();
        int counter2 = 0;
        theString.indexOf("the");

        if (theString.indexOf("the")!= -1)
        counter2++;



        System.out.printf("The characters 'the' were found %d times", counter2);
        System.out.println();

        System.out.println("This was programmed by -----");

Answer 1

您可以跟踪索引：

int index = theString.indexOf("the");
while(index >= 0) {
    index = theString.indexOf("the", index+1);
    counter2++;
}

Answer 2

你采取了一种复杂的方法。试试这个：

int count = str.split("the").length - 1;

如果您绝对必须使用indexOf()：

str = str.toLowerCase();
int count = 0;
for (int i = str.indexOf("the"); i >= 0; i = str.indexOf("the", i + 1))
    count++;

Answer 3

indexOf can take a second argument说明了从字符串开始的位置。因此，在找到第一个匹配项后，您可以告诉indexOf仅搜索该索引之后的字符串等。

此代码应该有效：

public static void main(String[] args) {
    String theString = "The other day I went over there.";
    theString = theString.toLowerCase();

    int index = -1;
    int count = 0;

    while (true) {
        index = theString.indexOf("the", index + 1);
        if (index == -1) {
            break;
        } else {
            count += 1;
        }
    }

    System.out.printf("The string 'the' was found %d times.\n", count);

    // Output:
    // The string 'the' was found 3 times.
}

Answer 4

indexOf(String str)方法查找str的第一个出现的索引。因此，如果你想找到{em> all str的出现，那么我建议你实现一个循环，一旦你找到str的实例，你就切断字符串str内theString再次theString，直到它不再在int index = theString.indexOf("the") int count = 0; while(index >= 0 && theString.length() > 0){ count++; theString = theString.substring(0, index + "the".length()); index = theString.indexOf("the"); }中。这是它应该是什么样子，

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Answer 5

如果你想特别使用indexOf（我认为这是一个赋值），你可以使用递归方法。

public static String numMatches (String str, String query) {
    int index = str.indexOf(query);
    if (index == -1) 
        return 0;
    else
        return 1 + numMatches(str.substring(index + query.length), query);
}

Answer 6

也许你可以做这样的事情，你可以使用indexOf（String str）

String word = "We are students of the Department of Informatics. All students should know how to program in Java and C.";

    int findit = word.indexOf("students");
    int count = 0;

    for(int i=0; i<=findit; i++)
    {

        findit = word.indexOf("students" , findit + 1);

        count = count + 1;

    }

    System.out.print(count);

Answer 7

这将检查字符串中出现的字符串数。

             String str = oIn.nextLine();
             String st = oIn.nextLine();
             int countS = 0;
             int index3 = str3.indexOf(st);
             while (index >= 0){
             index = str.indexOf(st, index+1);
             countS++;          
             }
             System.out.println("The number of occurrences of "+st +" in the string " +str3 +" are "+countS);

indexOf查找String中所有出现的单词

7 个答案: