如何在Java

Question

修復的空白文件IO我在Java編程新手和學習10。我正在製作一個簡單的RPG遊戲，但在我的代碼中遇到了問題。它是關於這個文件，當我完成運行它時，它是空白的。不知何故，當我運行它時，我得到一個空文件。有人能幫助我：c。 （抱歉壞英文）

這裏是我的代碼：FOR Random類

public class Dice { 
/** instance variables */ 
private final Random r; 

/** 
* Initializes the random number generator r 
*/ 


public Dice() { 
    r = new Random(); 
} 

/** 
* Returns a random integer between 1 and 6 using Random r 
* @return 
*/ 
public int roll() { 
    int dieRoll = r.nextInt(6 - 1); 
    return dieRoll; 
} 

}

FOR字符類

public class Character { 

static Dice dice = new Dice(); 
private String name; 
private int strength; 
private int dexterity; 
private int intelligence; 
private int maxLife; 
private int currentLife; 
private int atk; 

public Character(){ 

} 
public Character(String n, int s, int d, int i) { 

    this.name = n; 
    this.strength = s; 
    this.dexterity = d; 
    this.intelligence = i; 
    this.maxLife = 100 + dice.roll(); 
    this.currentLife = maxLife; 

} 


/** 
* Returns a random die roll using the roll method in the Dice.java, 
* *modified by the character's strength 
*/ 
public int attack() { 
    this.atk = strength * dice.roll() + 24; 
    return atk; 
} 

public void wound(int damage) { 
    if ((currentLife - damage) <= 0) { 
     this.currentLife = 0; 
    } else { 
     this.currentLife = currentLife - damage; 
    } 
} 

public void heal(int heal) { 
    if ((currentLife + heal) < maxLife) { 
     this.currentLife = currentLife + heal; 
    } else { 
     this.currentLife = maxLife; 
    } 
} 

public boolean checkDead() { 
    return currentLife == 0; 
} 

public String getName() { 
    return name; 
} 

public int getStrength() { 
    return strength; 
} 

/** 
* Returns dexterity 
*/ 
public int getDexterity() { 
    return dexterity; 
} 

/** 
* * Returns intelligence 
*/ 
public int getIntelligence() { 
    return intelligence; 
} 

/** 
* Returns currentLife 
*/ 
public int getCurrentLife() { 
    return currentLife; 
} 

/** 
* Returns maxLife 
*/ 
public int getMaxLife() { 
    return maxLife; 
} 

public int getAtk() { 
    return atk; 
} 

}

主類（這裏是WERE這個問題我不知道如果我缺少一些東西在這裏）

 public class TestCharacter { 
    public static void main(String letsPlay[]){ 
    PrintWriter outputStream = null; 
    try{ 
     outputStream = new PrintWriter(new FileOutputStream("RPGOutput.txt",true)); 

     Scanner s = new Scanner(System.in); 
    System.out.print("Enter Player 1 Character name:"); 
    Character p1 = new Character(s.next(),s.nextInt(),s.nextInt(),s.nextInt()); 
    System.out.println(p1.getName()+ "\tHAS ENTERED THE BATTLE!"); 
    System.out.println("Enter Player 2 Character name:"); 
    Character p2 = new Character(s.next(),s.nextInt(),s.nextInt(),s.nextInt()); 
    System.out.println(p2.getName()+ "\tHAS ENTERED THE BATTLE!");  

    int i = 1; 
    do { 
     outputStream.println("\nR O U N D " + i + "!"); 
     outputStream.print(p1.getName() + " "+"HP is"); 
     outputStream.println("\t" + p1.getCurrentLife() + "/" + p1.getMaxLife()); 
     outputStream.println("while"); 
     outputStream.print(p2.getName() + " " + " HP is"); 
     outputStream.println("\t" + p2.getCurrentLife() + "/" + p2.getMaxLife()); 
     outputStream.println(" "); 
     p2.wound(p1.attack()); 
     outputStream.println(p1.getName() + " attacks " + p2.getName() + " for " + p1.getAtk() + " damage!"); 
     if (p2.checkDead() == true) { 
      outputStream.println(p2.getName() + " lose " + p1.getName() + " has won!"); 
      return; 
     } 
     p1.wound(p2.attack()); 
     outputStream.println(p2.getName() + " attacks " + p1.getName() + " for " + p2.getAtk() + " damage!"); 
     if (p1.checkDead() == true) { 
      outputStream.println(p1.getName() + " lose " + p2.getName() + " has won!"); 
      return; 
     } 
     i++; 

    } while (p1.checkDead() == false || p2.checkDead() == false); 
    }catch(FileNotFoundException e){ 
     System.out.println("Error no file" + e); 
     System.exit(0); 
    } 
} 

}

Answer 1

當你打開一個流，你應該總是最後關閉它。

在java 1.7及以上版本中您只需try(... open the stream here){ ... useit ...}，編譯器添加了，最終隱式地關閉。

您需要終於接近，以確保你不要離開分配資源開放。

將PrintWriter設置爲自動刷新或確保在關閉流之前刷新是明智的，否則PrintWriter可能不會寫入輸出流，直到緩衝區已滿。

的Java 1.6及以下

OutputStream fos = null; 
    try{ 
     fos = new FileOutputStream("RPGOutput.txt",true); 
     PrintWriter out = new PrintWriter(fos, true); 

     out.println("Someting"); 
     out.println("..."); 

     // 
     out.flush(); 
    }catch(IOException e){ 
     // Manage exception 
    } finally { 
     try{ 
      if(fos!=null){ 
       fos.close(); 
      } 
     }catch(IOException e){ 
      // Swallow exception 
     } 
    } 

的Java 1.7及以上

try(OutputStream fos = new FileOutputStream("RPGOutput2.txt",true); 
      PrintWriter out = new PrintWriter(fos,true);) { 

     out.println("Hello"); 
     out.print("Hello 2"); 

    } catch (IOException e) { 
     // Manage exception 
    }