如果其他语句更有效

Question

我试图在java中重新创建一个打印机，我是相当新的编程，所以我在单个函数内部使用巨大的if else块来指示程序的逻辑，我注意到这是在同一个函数内部创建了大量的代码，我想知道是否有一个更有说服力的/有效的方法来做到这一点，下面的打印机类。打印机的逻辑并不太重要，但无论如何，只是一个不是双面打印机，逻辑负责检查墨粉量，确保打印的页面与双面打印机一致或不。

package com.company; 


public class Printer { 
private String name; 
private double tonerLevel = 100; 
private int ammountOfPaper; 
private int numberOfPagesPrinted; 
private boolean isDoubleSided; 

public Printer(String name, double tonerLevel, int ammountOfPaper, boolean isDoubleSided) { 
    this.name = name; 
    if(tonerLevel >= 0 && tonerLevel <= 100) { 
     this.tonerLevel = tonerLevel; 
    } 
    this.ammountOfPaper = ammountOfPaper; 
    this.isDoubleSided = isDoubleSided; 
} 

private boolean isOutOfToner(double numberToPrint) { 
    if((tonerLevel - (numberToPrint/2) < 0)) { 
     return true; 
    } 
    else { 
     return false; 
    } 
} 


private boolean isOutOfPaper(double numberToPrint) { 
    if(((ammountOfPaper - numberToPrint) < 0)) { 
     return true; 
    } 
    else { 
     return false; 
    } 
} 

private boolean twoSideNoPaperEven(double numberToPrint) { 
    if((ammountOfPaper - ((int) numberToPrint/2)) < 0) { 
     return true; 
    } 
    else { 
     return false; 
    } 
} 

private boolean twoSideNoPaperOdd(double numberToPrint) { 
    if(((ammountOfPaper - ((int) numberToPrint/2)) - 1) < 0) { 
     return true; 
    } 
    else { 
     return false; 
    } 
} 

public void printPages(double numberToPrint) { 

    if(isDoubleSided == false) { 
     if(tonerLevel == 0) { 
      System.out.println("Out of toner"); 
     } 
     if(ammountOfPaper == 0) { 
      System.out.println("Out of Paper"); 
     } 
     if(isOutOfToner(numberToPrint) && (tonerLevel != 0)) { 
      double difference = tonerLevel * 2; 
      numberToPrint = difference; 
      ammountOfPaper -= numberToPrint; 
      System.out.println("Will run out of toner after this print, able to print " + (int) numberToPrint + 
        " pages"); 
      tonerLevel = 0; 
     } 
     if(isOutOfPaper(numberToPrint) && (ammountOfPaper != 0)) { 
      double different = ammountOfPaper - numberToPrint; 
      numberToPrint = numberToPrint + different; 
      System.out.println("Will run out of paper after this print, printing " + (int) numberToPrint + " pages"); 
      ammountOfPaper = 0; 
     } 
     else if(!isOutOfToner(numberToPrint) && (!isOutOfPaper(numberToPrint))) { 
      ammountOfPaper -= numberToPrint; 
      tonerLevel = tonerLevel - (numberToPrint/2); 
      showPages(numberToPrint); 
     } 

    } 
    else if(isDoubleSided = true) { 
      if (numberToPrint % 2 == 0) { 
       if(tonerLevel == 0) { 
        System.out.println("Out of Toner"); 
       } 
       if(ammountOfPaper == 0) { 
        System.out.println("Out of Paper"); 
       } 
       if(twoSideNoPaperEven(numberToPrint) && (ammountOfPaper != 0)) { 
        ammountOfPaper -= numberToPrint/2; 
        System.out.println("There is no Paper"); 
       } 
       else if(!twoSideNoPaperEven(numberToPrint)) { 
        tonerLevel = tonerLevel - (numberToPrint/2); 
        ammountOfPaper -= numberToPrint/2; 
        showPages(numberToPrint); 
       } 
      } else { 
       if(tonerLevel == 0) { 
        System.out.println("Out of Toner"); 
       } 
       if(ammountOfPaper == 0) { 
        System.out.println("Out of Paper"); 
       } 
       if(twoSideNoPaperOdd(numberToPrint) && (ammountOfPaper != 0)) { 
        System.out.println("There is no paper"); 
        ammountOfPaper = (ammountOfPaper - ((int) numberToPrint/2)) - 1; 
        ammountOfPaper = 0; 
       } 
       else if(!twoSideNoPaperOdd(numberToPrint)) { 
        tonerLevel = tonerLevel - (numberToPrint/2); 
        ammountOfPaper = (ammountOfPaper - ((int) numberToPrint/2)) - 1; 
        showPages(numberToPrint); 
       } 
      } 
     } 

    } 

public void showPages(double numberToPrint) { 
    System.out.println("Printing " + (int) numberToPrint + " Pages, paper remaining is: " + this.ammountOfPaper 
      + " Toner level is: " + this.tonerLevel); 
} 

public void refillToner() { 
    tonerLevel = 100; 
} 
public void refillPaper(int paper) { 
    if(paper > 50) { 
     System.out.println("Cannot put in more paper"); 
    } 
    else { 
     this.ammountOfPaper += paper; 
    } 
} 

public int getAmmountOfPaper() { 
    return ammountOfPaper; 
} 

public double getTonerLevel() { 
    return tonerLevel; 
} 

public void setTonerLevel(double tonerLevel) { 
    this.tonerLevel = tonerLevel; 
} 

public void setAmmountOfPaper(int ammountOfPaper) { 
    this.ammountOfPaper = ammountOfPaper; 
} 

更改if语句由Nicolas的建议：

public void printPages(double numberToPrint) { 
if(tonerLevel == 0) { 
     System.out.println("Out of toner"); 
     return; 
    } 
    if(ammountOfPaper == 0) { 
     System.out.println("Out of Paper"); 
     return; 
    } 

if(isDoubleSided == false) { 

Answer 1

1. 你if-statements是多余的。您可以直接返回布尔值。它可以节省您的代码中的12行。例如：

   private boolean twoSideNoPaperOdd(double numberToPrint) { 
       return ((ammountOfPaper - ((int) numberToPrint/2)) - 1) < 0; 
   } 
   

2. 有很少的条件经常重复，相同的结果。再次，它将班级缩短24行。

   if (tonerLevel == 0) { 
       System.out.println("Out of toner"); 
       return; // leave the rest of method 
   } 
   
   if (ammountOfPaper == 0) { 
       System.out.println("Out of Paper"); 
       return 
   }