可比compareTo函数

Question

我想要有一个类似的函数compareTo两个街道地址。我目前正在研究地址的字符串(街道名称)。到目前为止，我有以下代码。我最终也希望能够比较街道号码，但我希望能够首先修复这个代码。每当我试图编译这段代码时，我都会得到以下错误：

StreetAddress.java:45: error: constructor StreetAddress in class StreetAddress cannot be applied to given types;
    StreetAddress add1 = new StreetAddress("cartesian road");
                         ^
  required: no arguments
  found: String
  reason: actual and formal argument lists differ in length
StreetAddress.java:46: error: constructor StreetAddress in class StreetAddress cannot be applied to given types;
    StreetAddress add2 = new StreetAddress("cartesian road");
                         ^
  required: no arguments
  found: String
  reason: actual and formal argument lists differ in length
StreetAddress.java:47: error: constructor StreetAddress in class StreetAddress cannot be applied to given types;
    StreetAddress add3 = new StreetAddress("n kings street");
                         ^
  required: no arguments
  found: String
  reason: actual and formal argument lists differ in length
StreetAddress.java:48: error: constructor StreetAddress in class StreetAddress cannot be applied to given types;
    StreetAddress add4 = new StreetAddress("pioneer parkway");
                         ^
  required: no arguments
  found: String
  reason: actual and formal argument lists differ in length
StreetAddress.java:49: error: constructor StreetAddress in class StreetAddress cannot be applied to given types;
    StreetAddress add5 = new StreetAddress("starry avenue");
                         ^
  required: no arguments
  found: String
  reason: actual and formal argument lists differ in length
5 errors

public class StreetAddress implements Comparable<StreetAddress>
{
protected int num;
protected String stName;

public void StreetAddress(int n, String s){
num = n;
stName = s;
}

public int getNum(){
    // returns the street number
    return num;
}

public String getName(){
    // returns the street name
    return stName;
}

public int compareTo(StreetAddress street) throws ClassCastException{
    // exception prevents crash if an address is not compared to
    // another address
    StreetAddress x = (StreetAddress) street;
    int compareName = this.stName.compareTo(street.stName); 
    if (compareName < 0){
        // first address comes after compared address
        System.out.println("test<0");
    }

    else if (compareName == 0){
        // same address
        System.out.println("test equal");
    }

    else{
        // first address comes before compared address
        System.out.println("test > 0");
    }

    }

public static void main(String args[])
{
StreetAddress add1 = new StreetAddress("cartesian road");
StreetAddress add2 = new StreetAddress("cartesian road");
StreetAddress add3 = new StreetAddress("n kings street");
StreetAddress add4 = new StreetAddress("pioneer parkway");
StreetAddress add5 = new StreetAddress("starry avenue");
add1.compareTo(add2);
add4.compareTo(add1);
add3.compareTo(add3);
add2.compareTo(add5);
}
}

Answer 1

正如你所指出的，问题是：

compareName == this.stName - (street.stName);

你不能减去字符串。我认为你要找的结果是：

int result = this.stName.compareTo(street.stName);

显然，这假定stName是一个String。如果不是，您必须在类compareTo中实现stName，就像我在编辑中看到的那样。您在编辑时报告的问题是，该类如下：

class StreetName {
    // Constructor
    StreetName(int n, String st) {
         // code
    }
}

但是，您正在尝试实例化类，如下所示：

StreetName fred = new StreetName("name");

您只向构造函数发送String，而不是向它发送int。假设数字很重要，您需要将其更改为：

StreetName fred = new StreetName(number, "name");

Answer 2

从另一个字符串中减去一个字符串意味着什么？这不太合理。相反，在这个位置调用String自己的compareTo(...)方法如何？另外，==运算符不应该在那里：

int compareName = stName.compareTo(street.stName);

另外，您的compareTo方法被定义为返回一个int，所以最好返回该int。现在它没有归还任何东西。