Java中由substring方法引发的内存泄漏详解

String x= "abcdef";
x= str.substring(1,3);
System.out.println(x);

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); //使用的是和父字符串同一个char数组value
 }

String(int offset, int count, char value[]) {
 this.value = value;
 this.offset = offset;
 this.count = count;
 }

String str = "abcdefghijklmnopqrst";
String sub = str.substring(1, 3);
str = null;

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

public String(char value[], int offset, int count) {
 if (offset < 0) {
 throw new StringIndexOutOfBoundsException(offset);
 }
 if (count < 0) {
 throw new StringIndexOutOfBoundsException(count);
 }
 // Note: offset or count might be near -1>>>1.
 if (offset > value.length - count) {
 throw new StringIndexOutOfBoundsException(offset + count);
 }
 this.value = Arrays.copyOfRange(value, offset, offset+count);
 }

public static char[] copyOfRange(char[] original, int from, int to) {
 int newLength = to - from;
 if (newLength < 0)
  throw new IllegalArgumentException(from + " > " + to);
 char[] copy = new char[newLength]; //是创建了一个新的char数组
 System.arraycopy(original, from, copy, 0,
    Math.min(original.length - from, newLength));
 return copy;
 }