Java代码没有按预期执行

-1

我写了一些Java代码，如下所示，但它不像我预期的那样运行。靠近底部，从if (upgrade == "Y")行开始。我做了一个测试，我输入了Y，但是这行并没有执行。你能帮我弄清楚为什么会发生这种行为吗？Java代码没有按预期执行

import java.io.*; 

class P4 
{ 
public static int get_price(String day_of_week, String age_group) 
{ 
    int price=0; 

    if (day_of_week == "WD") 
    { 
     if (age_group == "adult") 
      price = 66; 

     else if (age_group == "child") 
      price=48; 

     else 
      price = 32; 
    } 
    else 
    { 
     if (age_group == "adult") 
      price = 72; 

     else if (age_group == "child") 
      price=52; 

     else 
      price = 36; 
    } 

    return price; 
} 

public static void main(String[] args) 
{ 
    String adult2=null; 
    String child2=null; 
    String senior2=null; 
    String day_of_week=null; 
    String upgrade=null; 


    System.out.println("Enter Number of Adult Ticket:"); 
    BufferedReader adult1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     adult2 = adult1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    System.out.println("Enter Number of Child Ticket:"); 
    BufferedReader child1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     child2 = child1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    System.out.println("Enter Number of Senior Ticket:"); 
    BufferedReader senior1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     senior2 = senior1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    System.out.println("Choose Weekday or Weekend Pass (WD/WE):"); 
    BufferedReader day_of_week1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     day_of_week = day_of_week1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    System.out.println("Upgrade to Express Pass (Y/N):"); 
    BufferedReader upgrade1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     upgrade = upgrade1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    int adult = Integer.parseInt(adult2); 
    int child = Integer.parseInt(child2); 
    int senior = Integer.parseInt(senior2); 

    int total_a = adult * get_price(day_of_week, "adult"); 
    int total_c = child * get_price(day_of_week, "child"); 
    int total_s = senior * get_price(day_of_week, "senior"); 

    int total_price = total_a + total_c + total_s; 

    int total_people = adult + child + senior; 

    int upgrade_price = 0; 

    if (upgrade == "Y") 
    { 
     if (day_of_week == "WD") 
     { 
      upgrade_price = total_people * 30; 
     } 
     else 
     { 
      upgrade_price = total_people * 68; 
     } 
    } 
    else 
     upgrade_price = 0; 


    int price = upgrade_price + total_price; 

    System.out.println("The total price is $" + price); 

}}

来源

2012-01-20 Leo Jw

==仅用于比较引用在你的情况等于（）将是正确的选择....你的IDE的调试功能（如果你有任何使用），将使你的生活更容易这些情况.....你不仅会了解你的程序的工作，而且还会减少解决错误所需的时间...... – aProgrammer

我真的，真的推荐Joshua Block：用于学习java的“Effective Java”成语如何如何比较对象。 HTTP：//java.sun。com/docs/books/effective/ –

尝试使用.equal ..所以，如果其他（age_group.equals（ “子”）

时退房.equals（）方法：http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/String.html#equals(java.lang.Object)

和。 equalsIgnoreCase（）方法： http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/String.html#equalsIgnoreCase(java.lang.String)

import java.io.*; 

class P4 
{ 
    public static int get_price(String day_of_week, String age_group) 
    { 
    int price=0; 

    if (day_of_week.equals("WD")) 
    { 
     if (age_group.equals("adult")) 
     price = 66; 
     else if (age_group.equals("child")) 
     price=48; 
     else 
     price = 32; 
    } 
    else 
    { 
     if (age_group.equals("adult")) 
     price = 72; 
     else if (age_group.equals("child")) 
     price=52; 
     else 
     price = 36; 
    } 

    return price; 
}

来源

2012-01-20 07:05:25 technocrat

对于字符串中的平等条件，您需要equal方法。

，而不是使用

"Y".equals(upgrade); //is a good idea

upgrade == "Y"

因为字符串是对象，如果两个字符串具有相同的对象的equals（Object）方法将返回true。 ==运算符只有在两个String引用指向相同的底层String对象时才会成立。因此，当通过equals（Object）方法进行测试时，表示相同内容的两个字符串将相等，但如果它们实际上是同一个对象，那么在使用==运算符进行测试时只会相等。

参考http://blog.enrii.com/2006/03/15/java-string-equality-common-mistake/

来源

2012-01-20 07:05:23

我们必须首先为字符串比较例如 –

好吧......但在我的公共静态诠释get_price（）如果day_of_week ==“WD”的作品。任何想法为什么？ –

尝试升级==“是”它不会工作==只有当两个字符串引用指向相同的基础字符串对象时，==运算符才为真 –

你不能比较==字符串，你需要使用equals()

if("Y".equals(upgrade))

（我倾向于把恒定的第一，处理情况upgrade == null）

来源

2012-01-20 07:07:03

+1 StringLiteral.equals（variable） – Jeffrey

在java string comparison

String s = "something", t = "maybe something else"; 
    if (s == t)  // Legal, but usually WRONG. 
    if (s.equals(t)) // RIGHT 
    if (s > t) // ILLEGAL 
    if (s.compareTo(t) > 0) // CORRECT>

所以你的情况，使用：

if(upgrade.equals("Y")) { 
     //your codes 
}

import java.io.*; 

class P4 
{ 
public static int get_price(String day_of_week, String age_group) 
{ 
    int price=0; 

    if (day_of_week.equals("WD")) 
    { 
     if (age_group.equals("adult")) 
      price = 66; 

     else if (age_group.equals("child")) 
      price=48; 

     else 
      price = 32; 
    } 
    else 
    { 
     if (age_group.equals("adult")) 
      price = 72; 

     else if (age_group.equals("child")) 
      price=52; 

     else 
      price = 36; 
    } 

    return price; 
} 

public static void main(String[] args) 
{ 
    String adult2=null; 
    String child2=null; 
    String senior2=null; 
    String day_of_week=null; 
    String upgrade=null; 


    System.out.println("Enter Number of Adult Ticket:"); 
    BufferedReader adult1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     adult2 = adult1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    System.out.println("Enter Number of Child Ticket:"); 
    BufferedReader child1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     child2 = child1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    System.out.println("Enter Number of Senior Ticket:"); 
    BufferedReader senior1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     senior2 = senior1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    System.out.println("Choose Weekday or Weekend Pass (WD/WE):"); 
    BufferedReader day_of_week1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     day_of_week = day_of_week1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    System.out.println("Upgrade to Express Pass (Y/N):"); 
    BufferedReader upgrade1 = new BufferedReader(new InputStreamReader(System.in)); 
    try 
    { 
     upgrade = upgrade1.readLine();  
    } 
    catch (IOException e) { 
     System.out.println("Error!"); 
     System.exit(1); 
    } 

    int adult = Integer.parseInt(adult2); 
    int child = Integer.parseInt(child2); 
    int senior = Integer.parseInt(senior2); 

    int total_a = adult * get_price(day_of_week, "adult"); 
    int total_c = child * get_price(day_of_week, "child"); 
    int total_s = senior * get_price(day_of_week, "senior"); 

    int total_price = total_a + total_c + total_s; 

    int total_people = adult + child + senior; 

    int upgrade_price = 0; 

    if (upgrade.equals("Y")) 
    { 
     if (day_of_week.equals("WD")) 
     { 
      upgrade_price = total_people * 30; 
     } 
     else 
     { 
      upgrade_price = total_people * 68; 
     } 
    } 
    else 
     upgrade_price = 0; 


    int price = upgrade_price + total_price; 

    System.out.println("The total price is $" + price); 

}}

来源

2012-01-20 07:09:18 footy

我notised你update变量是字符串，因此，你应该使用：

if (upgrade.compareTo("Y") == 0) { 
     //your code 
    }

这是比较字符串的正确方法。

来源

2012-01-20 07:14:00 karla

我刚刚测试了您的代码上面和它的工作。您也可以使用upgrade.compareToIgnoreCase（“Y”）== 0 – karla

Java代码没有按预期执行

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