1 package junit.framework; 2 3 public class ComparisonCompactor { 4 5 private static final String ELLIPSIS = "..."; 6 private static final String DELTA_END = "]"; 7 private static final String DELTA_START = "["; 8 9 private int fContextLength; 10 private String fExpected; 11 private String fActual; 12 private int fPrefix; 13 private int fSuffix; 14 ComparisonCompactor(int contextLength, String expected, String actual)15 public ComparisonCompactor(int contextLength, String expected, String actual) { 16 fContextLength = contextLength; 17 fExpected = expected; 18 fActual = actual; 19 } 20 compact(String message)21 public String compact(String message) { 22 if (fExpected == null || fActual == null || areStringsEqual()) { 23 return Assert.format(message, fExpected, fActual); 24 } 25 26 findCommonPrefix(); 27 findCommonSuffix(); 28 String expected = compactString(fExpected); 29 String actual = compactString(fActual); 30 return Assert.format(message, expected, actual); 31 } 32 compactString(String source)33 private String compactString(String source) { 34 String result = DELTA_START + source.substring(fPrefix, source.length() - fSuffix + 1) + DELTA_END; 35 if (fPrefix > 0) { 36 result = computeCommonPrefix() + result; 37 } 38 if (fSuffix > 0) { 39 result = result + computeCommonSuffix(); 40 } 41 return result; 42 } 43 findCommonPrefix()44 private void findCommonPrefix() { 45 fPrefix = 0; 46 int end = Math.min(fExpected.length(), fActual.length()); 47 for (; fPrefix < end; fPrefix++) { 48 if (fExpected.charAt(fPrefix) != fActual.charAt(fPrefix)) { 49 break; 50 } 51 } 52 } 53 findCommonSuffix()54 private void findCommonSuffix() { 55 int expectedSuffix = fExpected.length() - 1; 56 int actualSuffix = fActual.length() - 1; 57 for (; actualSuffix >= fPrefix && expectedSuffix >= fPrefix; actualSuffix--, expectedSuffix--) { 58 if (fExpected.charAt(expectedSuffix) != fActual.charAt(actualSuffix)) { 59 break; 60 } 61 } 62 fSuffix = fExpected.length() - expectedSuffix; 63 } 64 computeCommonPrefix()65 private String computeCommonPrefix() { 66 return (fPrefix > fContextLength ? ELLIPSIS : "") + fExpected.substring(Math.max(0, fPrefix - fContextLength), fPrefix); 67 } 68 computeCommonSuffix()69 private String computeCommonSuffix() { 70 int end = Math.min(fExpected.length() - fSuffix + 1 + fContextLength, fExpected.length()); 71 return fExpected.substring(fExpected.length() - fSuffix + 1, end) + (fExpected.length() - fSuffix + 1 < fExpected.length() - fContextLength ? ELLIPSIS : ""); 72 } 73 areStringsEqual()74 private boolean areStringsEqual() { 75 return fExpected.equals(fActual); 76 } 77 } 78