看 - else if 語句：我把它放在哪里

Question

我不知道把我的 ELSE 語句放在哪里，如果我把它放在 for 循環中，在 IF 語句之后，它會多次重復 else 語句中的內容。 但是，如果我在 ELSE 語句中輸入想要輸出的內容，例如在 FOR 循環外“抱歉，無法找到此登記牌”，那么它會在我不想要的時候輸出。

    else // or 
            {
                // this code reads a file in
                String full="";
                try { FileReader reader = new FileReader("address.txt"); // new file reader to read in a file called address
                BufferedReader OwnerDetails = new BufferedReader(reader); // reads in the file efficiently

                String line; // assigning a string
                while ((line = OwnerDetails.readLine()) != null) { // reads in all file
                    full=full+line;

                }
                reader.close(); // the reader close, it finishes reading it in
                } catch (IOException e) {
                    e.printStackTrace();
                }
                //System.out.println(full); // reads in whole file, and outputs it, used to check if the file had been written in
                    // it is commented out once program is finished, but is used when testing
                String[] details = full.split(","); // splits up info into arrays

                String searchword=registration; // searchword is set as the registration plate entered
                for (int i=0;i<details.length-2;i=i+1) 
                {
                    if(searchword.equals(details[i])) // if the search word is in the file
                    {
                        System.out.println("Name: " +details[i-1]); // outputs name
                        System.out.println("Registration: "+details[i]); // outputs reg plate again 
                        System.out.println("Address Line 1: "+details[i+1]); // outputs address
                        System.out.println("Address Line 2: "+details[i+2]); // outputs address line 2

                        fw2.write(details[i-1]+","); // separates the details when writing in to the file
                        fw2.write(details[i]+",");
                        fw2.write(details[i+1]+",");
                        fw2.write(details[i+2]+",");
                        fw2.write(speed+"/n");
                        fw2.close(); // file writer closes

                    }
                }

                System.out.println("The numberplate entered could not be found in the file, sorry."); // outputted if registration is not found
            }

任務是在文件中搜索車牌，如果它不在文件中，那么它應該輸出它不在文件中。

上面代碼的輸出是： the speed the car was driving at was: 39.47 mph Name: Adam Davies Registration: AA12ASD Address Line 1: 1 New Road Address Line 2: Northfleet The numberplate entered could not be found in the file, sorry.

Answer 1

所以我要做的方法是添加一個布爾值檢查是否找到了詳細信息。

從一開始就制作它並將其設置為false 。 那么當

if(searchword.equals(details[i]))

使布爾值true 。 在 for 循環之后，檢查布爾值是否為false ，如果為false ，請打印您抱歉找不到這個登記牌

下面的一個簡單示例如下所示：

boolean yes = false;
    for (int i=0;i<details.length-2;i=i+1){
        if(searchword.equals(details[i])){
            System.out.println("Name: " +details[i-1]);
            yes = true;
        }
    }
    if (!yes){
        System.out.println("sorry this registration plate couldn't be found")
    }
}

Answer 2

如果我正確收集了它，代碼的目的是查找文本文件中是否存在特定的注冊號。 為此，您將整個文件內容讀入一個字符串並將其拆分為, 。 然后使用for loop遍歷整個數組並查找您擁有的特定注冊號，即searchword 。

為了記錄，我並不完全相信您實施它的方式（本來可以更好，我不會涉及）。 但是，按照您實施的方式，您的方法的問題在於您正在執行在for loop中搜索key的操作，並嘗試在循環本身中執行if-else部分。

這就是你如何做你需要的。

    String a = "Hello,World,Foo,Bar,abc,def,ghi,Hello1,World1,Foo1,Bar1,abc,def,ghi";
    String[] b = a.split(",");
    String searchWord = "abc";

    boolean hasSearchWord = false;

    for(int i = 0; i < b.length; i++) {
        if(b[i].equals(searchWord)) {
            hasSearchWord = true;
            System.out.println("Word found");
            // Print whatever you need
            System.out.println(b[i - 1]);
            System.out.println(b[i]);
            System.out.println(b[i + 1]);
        }
    }

    if(!hasSearchWord) {
        System.out.println("Word not found");
    }

搜索abc ，這將產生

Word found
Bar
abc
def
Word found
Bar1
abc
def

搜索duh ，這將產生

Word not found