JAVA - LString Java、リンクされた文字列

Question

私のプログラムでは、入力または出力を持たないLString.javaを持っていますが、コンパイルのテスト方法はLStringTest.javaです。このプログラムはjunit.jarも実行します。

私のプログラムは上半期にはうまくいくが、私には何をしているのか、どうやって解決するのか正確にはわからないというエラーメッセージが出るようになる。私の質問は、私のプログラムがエラーのないテストの残りの部分を実行できるように、どうすればこれらのエラーを解決するのだろうかと思います。前もって感謝します！ 、LString.javaここ

---

----jGRASP exec: java LStringTest 
Running constructor, length, toString tests (10 tests) 
Starting tests: .......... 
Time: 0.010 
OK! (10 tests passed.) 

Running compareTo and equals tests (18 tests) 
Starting tests: .................. 
Time: 0.022 
OK! (18 tests passed.) 

Running charAt and setCharAt tests (18 tests) 
Starting tests: .................. 
Time: 0.032 
OK! (18 tests passed.) 

Running substring tests (63 tests) 
Starting tests: ............................................................... 
Time: 0.076 
OK! (63 tests passed.) 

Running replace tests (31 tests) 
Starting tests: E...EEE....EEEEEEE...EEEEEEE... 
Time: 0.046 

There were 18 failures: 
1) test61aReplaceEmptyString(LStringTest$LStringReplaceTestSpecial) 
java.lang.NullPointerException 
     at LString.replace(LString.java:171) 
     at LStringTest$LStringReplaceTestSpecial.test61aReplaceEmptyString(LStringTest.java:553) 
     ... 10 more 
2) test63aReplaceOneChar(LStringTest$LStringReplaceTestSpecial) 
java.lang.NullPointerException 
     at LString.replace(LString.java:190) 
     at LStringTest$LStringReplaceTestSpecial.test63aReplaceOneChar(LStringTest.java:576) 
     ... 10 more 
3) test63bReplaceOneChar(LStringTest$LStringReplaceTestSpecial) 
java.lang.AssertionError: replace returned different LString expected same:<a> was not:<axyzzy> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTestSpecial.test63bReplaceOneChar(LStringTest.java:587) 
     ... 10 more 
4) test63cReplaceOneChar(LStringTest$LStringReplaceTestSpecial) 
org.junit.ComparisonFailure: Replace of One Character LString is wrong expected:<[]xyzzy> but was:<[a]xyzzy> 
     at org.junit.Assert.assertEquals(Assert.java:115) 
     at LStringTest$LStringReplaceTestSpecial.test63cReplaceOneChar(LStringTest.java:593) 
     ... 10 more 
5) test71aReplacePrepend[0](LStringTest$LStringReplaceTest) 
java.lang.NullPointerException 
     at LString.replace(LString.java:190) 
     at LStringTest$LStringReplaceTest.test71aReplacePrepend(LStringTest.java:660) 
     ... 10 more 
6) test71bReplaceAppend[0](LStringTest$LStringReplaceTest) 
java.lang.AssertionError: replace returned different LString expected same:<abcd> was not:<abcdxyzzy> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTest.test71bReplaceAppend(LStringTest.java:673) 
     ... 10 more 
7) test71cReplaceInMiddle[0](LStringTest$LStringReplaceTest) 
java.lang.AssertionError: replace returned different LString expected same:<abcd> was not:<abxyzzycd> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTest.test71cReplaceInMiddle(LStringTest.java:683) 
     ... 10 more 
8) test71dReplaceAtStart[0](LStringTest$LStringReplaceTest) 
java.lang.NullPointerException 
     at LString.replace(LString.java:190) 
     at LStringTest$LStringReplaceTest.test71dReplaceAtStart(LStringTest.java:690) 
     ... 10 more 
9) test71eReplaceAtEnd[0](LStringTest$LStringReplaceTest) 
java.lang.AssertionError: replace returned different LString expected same:<abcd> was not:<abxyzzy> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTest.test71eReplaceAtEnd(LStringTest.java:703) 
     ... 10 more 
10) test71fReplaceInMiddle[0](LStringTest$LStringReplaceTest) 
java.lang.AssertionError: replace returned different LString expected same:<abcd> was not:<abxyzzycd> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTest.test71fReplaceInMiddle(LStringTest.java:713) 
     ... 10 more 
11) test71gReplaceAll[0](LStringTest$LStringReplaceTest) 
org.junit.ComparisonFailure: replace(0, length) is wrong expected:<[]xyzzy> but was:<[a]xyzzy> 
     at org.junit.Assert.assertEquals(Assert.java:115) 
     at LStringTest$LStringReplaceTest.test71gReplaceAll(LStringTest.java:721) 
     ... 10 more 
12) test71aReplacePrepend[1](LStringTest$LStringReplaceTest) 
java.lang.NullPointerException 
     at LString.replace(LString.java:190) 
     at LStringTest$LStringReplaceTest.test71aReplacePrepend(LStringTest.java:660) 
     ... 10 more 
13) test71bReplaceAppend[1](LStringTest$LStringReplaceTest) 
java.lang.AssertionError: replace returned different LString expected same:<Yet another even longer string.> was not:<Yet another even longer string.xyzzy> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTest.test71bReplaceAppend(LStringTest.java:673) 
     ... 10 more 
14) test71cReplaceInMiddle[1](LStringTest$LStringReplaceTest) 
java.lang.AssertionError: replace returned different LString expected same:<Yet another even longer string.> was not:<Yet another evexyzzyn longer string.> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTest.test71cReplaceInMiddle(LStringTest.java:683) 
     ... 10 more 
15) test71dReplaceAtStart[1](LStringTest$LStringReplaceTest) 
java.lang.NullPointerException 
     at LString.replace(LString.java:190) 
     at LStringTest$LStringReplaceTest.test71dReplaceAtStart(LStringTest.java:690) 
     ... 10 more 
16) test71eReplaceAtEnd[1](LStringTest$LStringReplaceTest) 
java.lang.AssertionError: replace returned different LString expected same:<Yet another even longer string.> was not:<Yet another evexyzzy> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTest.test71eReplaceAtEnd(LStringTest.java:703) 
     ... 10 more 
17) test71fReplaceInMiddle[1](LStringTest$LStringReplaceTest) 
java.lang.AssertionError: replace returned different LString expected same:<Yet another even longer string.> was not:<Yet anotxyzzy string.> 
     at org.junit.Assert.fail(Assert.java:88) 
     at org.junit.Assert.failNotSame(Assert.java:737) 
     at org.junit.Assert.assertSame(Assert.java:680) 
     at LStringTest$LStringReplaceTest.test71fReplaceInMiddle(LStringTest.java:713) 
     ... 10 more 
18) test71gReplaceAll[1](LStringTest$LStringReplaceTest) 
org.junit.ComparisonFailure: replace(0, length) is wrong expected:<[]xyzzy> but was:<[Y]xyzzy> 
     at org.junit.Assert.assertEquals(Assert.java:115) 
     at LStringTest$LStringReplaceTest.test71gReplaceAll(LStringTest.java:721) 
     ... 10 more 

Test Failed! (18 of 31 tests failed.) 

Test failures: abandoning other phases. 

----jGRASP wedge: exit code for process is 1. 
----jGRASP: operation complete. 

が私のコードです：

以下

は、それが私に与えていることをこれまでの私のコードの出力との誤差である

import java.io.*; 
import java.util.*; 

public class LString { 

    node front; 
    int size; 

    // Creating a node class 
    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; 
      } 

    } 

    // Constructors 
    public LString(){ 
      this.size = 0; 
      this.front = null; 
    } 

    public LString(String original) { 
      this.size = original.length(); 
      if (original.length() > 0) { 

       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; 
       } 
      } 
    } 

    // Length method, returns the length of LString 
    public int length() { 
     return this.size; 
    } 

    // compareTo method, compares this LString to anotherLString, returns 0 if equal, 
    // -1 if lexicogrpahically less, and 1 if lexicographically greater 
    public int compareTo(LString anotherLString) { 
     int len1 = length(); 
     int len2 = anotherLString.length(); 
     int lim = Math.min(len1, len2); 

     node cn1 = front; 
     node cn2 = anotherLString.front; 

     int k = 0; 
     while (k < lim) { 
      char c1 = cn1.data; 
      char c2 = cn2.data; 
      if (c1 != c2) { 
       return c1-c2; 
      } 
      k++; 
      cn1 = cn1.next; 
      cn2 = cn2.next; 
     } 

     return len1 - len2; 
    } 

    // a boolean equals method that returns true if LString and other are the same, false if not 
    public boolean equals(Object other) { 
     if (this == other) { 
      return true; 
     } 

     if (other instanceof LString) { 
      LString otherLString = (LString)other; 
      int n = length(); 
      if (n == otherLString.length()) { 
       node n1 = front; 
       node n2 = otherLString.front; 

       while (n1 != null) { 
        if (n1.data != n2.data) { 
         return false; 
        } 
        n1 = n1.next; 
        n2 = n2.next; 
       } 
       return true; 
      } 
     } 

     return false; 
    } 


    // charAt returns the character of LString at the argument index 
    public char charAt(int index) { 

     if ((index < 0) || (index >= this.length())) { 
      throw new IndexOutOfBoundsException(); 
     } 

     node curNode = front; 
     for (int i = 0; i < this.length(); i++, curNode = curNode.next) { 
      if (i == index) { 
       return curNode.data; 
      } 
     } 

     throw new IllegalStateException(); 
    } 

    public void setCharAt(int index, char ch) { 
     if (index < 0 || index >= this.length()) { 
     throw new IndexOutOfBoundsException(); 
     } 

     else { 
     node currNode = front; 
     for (int i = 0; i <this.length(); i++, currNode = currNode.next) { 
      if (i == index) { 
      currNode.data = ch; 
      } 
     } 
     } 
    } 

    public LString substring(int start, int end) { 
     if (start < 0 || end > this.length() || start > end) { 
     throw new IndexOutOfBoundsException(); 
     } 

     LString substring = new LString(); 
     if (start == end) { 
     return substring; 
     } 
     node node = this.front; 
     for (int i = 0; i < start; i++) { 
     node = node.next; 
     } 

     node copy = new node(node.data); 
     substring.front = copy; 
     for (int i = start+1; i < end; i++) { 
     node = node.next; 
     copy = copy.next = new node(node.data); 
     } 

     substring.size = end - start; 
     return substring;  
    } 

    public LString replace(int start, int end, LString lStr) { 
     if (start < 0 || end > length() || start > end) { 
     throw new IndexOutOfBoundsException(); 
    } 

    LString result = new LString(); 
    node node = this.front; 
    node copy = new node(node.data); 
     result.front = copy; 
    for (int i = 1; i < start; i++) { 
     node = node.next; 
     copy = copy.next = new node(node.data); 
    } 

    node replace = lStr.front; 
    for (int i = 0; i < lStr.length(); i++) { 
     copy = copy.next = new node(replace.data); 
     replace = replace.next; 
    } 

    for (int i = start; i < end; i++) { 
     node = node.next; 
    } 

    for (int i = end; i < length(); i++) { 
     node = node.next; 
     copy = copy.next = new node(node.data); 
    } 

    result.size = length() + lStr.length() - (end - start); 
    return result; 
} 

    public void append(char data) { 

     this.size++; 

     if (front == null) { 
      front = new node(data); 
      return; 
     } 

     node curr = front; 
     while (curr.next != null) { 
      curr = curr.next; 
     } 

     curr.next = new node(data); 

    } 

    public void prepend (char data) { 

     front = new node(data, front); 
     size++; 
    } 


    public void delete(int index) { 

     if (index == 0) { 
      front = front.next; 
     } else { 
      node curr = front; 
      for (int i = 0; i < index - 1; i++){ 
       curr = curr.next; 
      } 

      curr.next = curr.next.next; 
      } 

     size--; 
    } 

    public String toString() { 
     StringBuilder result = new StringBuilder(); 

     node curr = front; 
     while (curr != null) { 

      result.append(curr.data); 
      curr = curr.next; 
     } 

     return result.toString(); 
    } 

    public void add(int index, char data) { 
     if (index == 0) { 
       front = new node(data, front); 
     } else { 
       node curr = front; 
       for (int i = 0; i < index - 1; i++){ 
        curr = curr.next; 
       } 

       curr.next = new node(data, curr.next); 
      } 
     } 

    public void print() { 
    System.out.println(this.toString()); 

    } 
} 

---

@ScaryWombatのエラー1：

ここにコードeからLStringTest.java：

@Test public void test61aReplaceEmptyString() { 
     LString testLString = new LString(); 
     LString newLString = testLString.replace(0, 0, replaceLString); 
     assertEquals("Replace of Empty LString is wrong", 
       replaceString, newLString.toString()); 
     assertSame("replace returned different LString", testLString, newLString); 
     } 

これは、エラーを出すLString.javaのコードスニペットです。ライン171から...

LString result = new LString(); 
    node node = this.front; 
    node copy = new node(node.data); 
     result.front = copy; 

Answer 1

[OK]をあなたは

LString testLString = new LString(); 

を呼び出すとき、それはコンストラクタ

// Constructors 
public LString(){ 
     this.size = 0; 
     this.front = null; 
} 

はそのthis.frontを参照してください呼び出すtest61aReplaceEmptyStringでビット

これを破ることができますはnull

ですあなたは replaceでそれを見るだろう testLString.replace(0, 0, replaceLString);

を呼び出すとき

は今

node node = this.front; 

がthis.frontがところで今nodeもnull

で非常に混乱しているクラス名nullであることを覚えているコードがありますオブジェクト名は同じです。とにかく

、nodeはnullその後、

new node(node.data); 

あるよう

public LString replace(int start, int end, LString lStr) { 
    if (start < 0 || end > length() || start > end) { 
    throw new IndexOutOfBoundsException(); 
    } 

    if (this.front == null) { 
     return lStr; // maybe correct logic for you? 
    } 

（つまり、ノードがnullである）を使用すると、既存のLStringは先頭が空であるかどうかをテストする必要があり、それを修正するにはNPE

がスローされます