我在为构建字符串的链表对象编写 compareTo() 和 charAt() 方法时遇到问题。该类名为LString，包含一个构造函数和一些其他方法。它与另一个文件一起运行，该文件测试其作为链接列表字符串生成器的能力，并且我收到此错误消息:
Running constructor, length, toString tests (10 tests)
Starting tests: ..........
Time: 0.000
OK! (10 tests passed.)
Running compareTo and equals tests (18 tests)
Starting tests: EEEEEEEEEEEE......
Time: 0.015
There were 12 failures:
1) t21aTestCompareTo[0](LStringTest$LStringCompareToTest)
java.lang.AssertionError: compareTo of "abc" and "abd" wrong expected:<-1> but was:<0>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.junit.Assert.assertEquals(Assert.java:555)
at LStringTest$LStringCompareToTest.t21aTestCompareTo(LStringTest.java:259)
... 9 more
2) t22aTestEquals[0](LStringTest$LStringCompareToTest)
java.lang.AssertionError: equals of "abc" and "abd" wrong expected:<false> but was:<true>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at LStringTest$LStringCompareToTest.t22aTestEquals(LStringTest.java:269)
... 9 more
3) t21aTestCompareTo[1](LStringTest$LStringCompareToTest)
java.lang.AssertionError: compareTo of "a" and "" wrong expected:<1> but was:<0>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.junit.Assert.assertEquals(Assert.java:555)
at LStringTest$LStringCompareToTest.t21aTestCompareTo(LStringTest.java:261)
... 9 more
4) t22aTestEquals[1](LStringTest$LStringCompareToTest)
java.lang.AssertionError: equals of "" and "a" wrong expected:<false> but was:<true>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at LStringTest$LStringCompareToTest.t22aTestEquals(LStringTest.java:269)
... 9 more
5) t21aTestCompareTo[2](LStringTest$LStringCompareToTest)
java.lang.AssertionError: compareTo of "a" and "ab" wrong expected:<-1> but was:<0>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.junit.Assert.assertEquals(Assert.java:555)
at LStringTest$LStringCompareToTest.t21aTestCompareTo(LStringTest.java:259)
... 9 more
6) t22aTestEquals[2](LStringTest$LStringCompareToTest)
java.lang.AssertionError: equals of "a" and "ab" wrong expected:<false> but was:<true>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at LStringTest$LStringCompareToTest.t22aTestEquals(LStringTest.java:269)
... 9 more
7) t21aTestCompareTo[3](LStringTest$LStringCompareToTest)
java.lang.AssertionError: compareTo of "abc" and "abcd" wrong expected:<-1> but was:<0>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.junit.Assert.assertEquals(Assert.java:555)
at LStringTest$LStringCompareToTest.t21aTestCompareTo(LStringTest.java:259)
... 9 more
8) t22aTestEquals[3](LStringTest$LStringCompareToTest)
java.lang.AssertionError: equals of "abc" and "abcd" wrong expected:<false> but was:<true>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at LStringTest$LStringCompareToTest.t22aTestEquals(LStringTest.java:269)
... 9 more
9) t21aTestCompareTo[4](LStringTest$LStringCompareToTest)
java.lang.AssertionError: compareTo of "B" and "a" wrong expected:<-1> but was:<0>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.junit.Assert.assertEquals(Assert.java:555)
at LStringTest$LStringCompareToTest.t21aTestCompareTo(LStringTest.java:259)
... 9 more
10) t22aTestEquals[4](LStringTest$LStringCompareToTest)
java.lang.AssertionError: equals of "B" and "a" wrong expected:<false> but was:<true>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at LStringTest$LStringCompareToTest.t22aTestEquals(LStringTest.java:269)
... 9 more
11) t21aTestCompareTo[5](LStringTest$LStringCompareToTest)
java.lang.AssertionError: compareTo of "BB" and "Ba" wrong expected:<-1> but was:<0>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.junit.Assert.assertEquals(Assert.java:555)
at LStringTest$LStringCompareToTest.t21aTestCompareTo(LStringTest.java:259)
... 9 more
12) t22aTestEquals[5](LStringTest$LStringCompareToTest)
java.lang.AssertionError: equals of "BB" and "Ba" wrong expected:<false> but was:<true>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
at LStringTest$LStringCompareToTest.t22aTestEquals(LStringTest.java:269)
... 9 more
Test Failed! (12 of 18 tests failed.)
Test failures: abandoning other phases.
LString 类旨在模仿 Java 的 String 和 StringBuilder，但使用链接列表而不是数组。我对如何使用 this 关键字有点困惑。在下面的 compareTo() 方法中，我想象使用 this 时对自己说“如果此索引处的 LStrings 字符等于参数在同一索引处的 LString 字符，则返回 0”。
我正在引用此页面，但不确定如何有效地编写它:http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#compareTo%28java.lang.String%29
如果 LString 具有完全相同的字符，我希望 compareTo() 返回 0；如果此 LString 按字典顺序小于另一个 LString，则返回小于零的值；如果按字典顺序大于另一个 LString，则返回大于零的值。
public class LString {
node front;
int size;
private class node {
char data;
node next;
public node (){
}
public node (char newData){
this.data = newData;
}
public node (char newData, node newNext){
this.data = newData;
this.next = newNext;
}
}
public LString(){
this.size = 0;
this.front = null;
}
public LString(String original) {
this.size = original.length();
if (original != ""){
this.front = new node(original.charAt(0));
node curr = this.front;
for (int i =1; i < original.length(); i++) {
curr.next = new node(original.charAt(i));
curr = curr.next;
}
}
}
public int length() {
return this.size;
}
public int compareTo(LString anotherLString) {
for (int i = 0; i < this.length(); i++) {
if (this.charAt(i) == anotherLString.charAt(i)) {
return 0;
}
//other logic for returning 1 or -1
}
return this.length()-anotherLString.length();
}
public boolean equals(Object other) {
if (other == null || !(other instanceof LString)) {
return false;
}
else {
LString otherLString = (LString)other;
return true;
}
}
public char charAt(int index) {
//return this.charAt(index)?
}
}
这段代码中的相关方法尚未完成。任何建议都值得赞赏，正在努力学习 Java。
最佳答案
public int compareTo(LString anotherLString) {
for (int i = 0; i < this.length() && i<anotherLString.length(); i++) {
if (this.charAt(i) == anotherLString.charAt(i)) {
return 0;
}
else if(((int)this.charAt(i))<((int)anotherLString.charAt(i)))
return -1;
else
return 1;
}
return this.length()-anotherLString.length();
}
我认为这个解决方案应该可以满足您的要求。我已将 char 类型转换为 int，然后将它们与返回 -1/1 进行比较。此外，我还对 for 循环添加了长度限制。
注意:使用 charAt(index) 在这里不是有效的解决方案，因为每次获取字符时都会迭代链接列表。相反，您应该直接迭代链接列表以进行比较。
关于java - 为字符链接列表编写一个compareTo()方法，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/28823414/