Java 分析并解决内存泄漏的实例

jmap -dump:format=b,file=heap.bin <pid> 

public  
String[] split(String regex, int limit) { 
  return Pattern.compile(regex).split(this, limit); 
} 

public  
String[] split(CharSequence input, int limit) { 
    int index = 0; 
    boolean matchLimited = limit > 0; 
    ArrayList<String> matchList = new  
ArrayList<String>(); 
    Matcher m = matcher(input); 
    // Add segments before each match found 
    while(m.find()) { 
      if (!matchLimited || matchList.size() < limit - 1) { 
        String match = input.subSequence(index,  
m.start()).toString(); 
        matchList.add(match); 
        index = m.end(); 
      } else if (matchList.size() == limit - 1) { // last one 
        String match = input.subSequence(index, 
                          
input.length()).toString(); 
        matchList.add(match); 
        index = m.end(); 
      } 
    } 
    // If no match was found, return this 
    if (index == 0) 
      return new String[] {input.toString()}; 
    // Add remaining segment 
    if (!matchLimited || matchList.size() < limit) 
      matchList.add(input.subSequence(index,  
input.length()).toString()); 
    // Construct result 
    int resultSize = matchList.size(); 
    if (limit == 0) 
      while (resultSize > 0 &&  
matchList.get(resultSize-1).equals("")) 
        resultSize--; 
    String[] result = new String[resultSize]; 
    return matchList.subList(0, resultSize).toArray(result); 
  } 
  注意看第9行：Stirng match = input.subSequence(intdex, m.start()).toString();

public  
CharSequence subSequence(int beginIndex, int endIndex) { 
    return this.substring(beginIndex, endIndex); 
} 
  String.subSequence有调用了String.subString，继续看：

public String  
substring(int beginIndex, int endIndex) { 
  if (beginIndex < 0) { 
    throw new StringIndexOutOfBoundsException(beginIndex); 
  } 
  if (endIndex > count) { 
    throw new StringIndexOutOfBoundsException(endIndex); 
  } 
  if (beginIndex > endIndex) { 
    throw new StringIndexOutOfBoundsException(endIndex - beginIndex); 
  } 
  return ((beginIndex == 0) && (endIndex == count)) ? this : 
    new String(offset + beginIndex, endIndex - beginIndex, value); 
  } 

// Package  
private constructor which shares value array for speed. 
  String(int offset, int count, char value[]) { 
  this.value = value; 
  this.offset = offset; 
  this.count = count; 
  } 

  /** 
   * Initializes a newly created {@code String} object so that it 
represents 
   * the same sequence of characters as the argument; in other words, 
the 
   * newly created string is a copy of the argument string. Unless an 
   * explicit copy of {@code original} is needed, use of this 
constructor is 
   * unnecessary since Strings are immutable. 
   * 
   * @param original 
   *     A {@code String} 
   */ 
  public String(String original) { 
  int size = original.count; 
  char[] originalValue = original.value; 
  char[] v; 
  if (originalValue.length > size) { 
    // The array representing the String is bigger than the new 
    // String itself. Perhaps this constructor is being called 
    // in order to trim the baggage, so make a copy of the array. 
      int off = original.offset; 
      v = Arrays.copyOfRange(originalValue, off, off+size); 
  } else { 
    // The array representing the String is the same 
    // size as the String, so no point in making a copy. 
    v = originalValue; 
  } 
  this.offset = 0; 
  this.count = size; 
  this.value = v; 
  }