如何解決「變量phraseLength可能尚未初始化」（Java）？

Question

我是新編程的Java和涉及字符串的工作。我剛開始使用代碼模板，我的指令是編譯它並查看輸出，但是有一個錯誤提示「變量phraseLength可能沒有被初始化」。它指的是當我使用「phraseLength」作爲我的代碼底部附近的變量時。有誰知道如何解決這一問題？非常感謝你提前。

import java.util.Scanner; 
public class Working_With_Strings 
{ 
public static void main (String[] args) 
{ 
//instantiate the String…… 
String phrase = new String ("This is a String test."); 
int phraseLength; 
int middle3;// number of characters in the phrase String 
int middleIndex; // index of the middle character in the String 
String firstHalf; // first half of the phrase String 
String secondHalf; // second half of the phrase String 
String switchedPhrase; // a new phrase with original halves switched 

// 1-compute the length and middle index of the phrase 


//2- get the substring for each half of the phrase 


//3- concatenate the firstHalf at the end of the secondHalf 


    // print information about the phrase 
    System.out.println(); 
    System.out.println ("Original phrase: " + phrase); 
    System.out.println ("Length of the phrase: " + phraseLength + 
       " characters"); 
    System.out.println ("Index of the middle: " + middleIndex); 
    System.out.println ("Character at the middle index: " + 
       phrase.charAt(middleIndex)); 
    System.out.println ("Switched phrase: " + switchedPhrase); 

    System.out.println(); 
    } 
} 

我不明白錯誤是什麼意思，因爲我不知道初始化是什麼意思。現在我知道我需要用一個值初始化「phraseLength」。再次感謝你的幫助！

Answer 1

你聲明的變量和未初始化變量

int phraseLength;

，在這裏你試圖訪問未初始化的變量。

System.out.println ("Length of the phrase: " + phraseLength + 
       " characters"); 

必須訪問前值定義值的變量：

有兩個解決方案，你的情況：

1.You應該像聲明後初始化變量如下：

`int phraseLength;//Declaration 
pharaseLength = 0;`//Initialization 

2.通過s分配變量青梅計算：

在這裏，我走的是字符串的長度將其分配給變量

pharaseLength = pharaseString.length(); 

您需要爲其餘變量

供您參考做同樣的：

差異在Initialization , assignment ,declaration:之間 https://stackoverflow.com/a/2614178/5395773

Answer 2

int phraseLength; 
int middle3;// number of characters in the phrase String 
int middleIndex; // index of the middle character in the String 
String firstHalf; // first half of the phrase String 
String secondHalf; // second half of the phrase String 
String switchedPhrase; // a new phrase with original halves switched 

到：

int phraseLength = 0; 
int middle3 = 0;// number of characters in the phrase String 
int middleIndex = 0; // index of the middle character in the String 
String firstHalf = ""; // first half of the phrase String 
String secondHalf = ""; // second half of the phrase String 
String switchedPhrase = ""; // a new phrase with original halves switched 

你應該初始化變量之前使用它們......我推薦一本書給你的方法聲明Head First Java

Answer 3

變量不能自動初始化
。也許你需要閱讀一些關於java基礎知識的基本書籍。

int phraseLength = 0; 
int middle3 = 0;// number of characters in the phrase String 
int middleIndex = 0; // index of the middle character in the String 
String firstHalf = null; // first half of the phrase String 
String secondHalf = null; // second half of the phrase String 
String switchedPhrase = null; 

Answer 4

`  import java.util.Scanner; 
    public class Working_With_Strings 
    { 
    public static void main (String[] args) 
    { 
    //instantiate the String…… 
    String phrase = new String ("This is a String test."); 
    int phraseLength; 
    phraseLength=phrase.length(); 
    System.out.println ("Original phrase: " + phrase); 
    System.out.println ("Length of the phrase: " + phraseLength + 
       " characters"); 

    } 
    }  

      `