import sun.jvm.hotspot.oops.LineNumberTableElement; //导入依赖的package包/类
private SoftLocationXRefs getBaseLocations() {
    SoftLocationXRefs info = (softBaseLocationXRefsRef == null) ? null :
                                 (SoftLocationXRefs)softBaseLocationXRefsRef.get();
    if (info != null) {
        return info;
    }

    byte[] codeBuf = bytecodes();
    firstIndex = 0;
    lastIndex = codeBuf.length - 1;
    // This is odd; what is the Location of a Method?
    // A StackFrame can have a location, but a Method?
    // I guess it must be the Location for bci 0.
    location = new LocationImpl(virtualMachine(), this, 0);

    boolean hasLineInfo = saMethod.hasLineNumberTable();
    LineNumberTableElement[] lntab = null;
    int count;

    if (hasLineInfo) {
        lntab = saMethod.getLineNumberTable();
        count = lntab.length;
    } else {
        count = 0;
    }

    List lineLocations = new ArrayList(count);
    Map lineMapper = new HashMap();
    int lowestLine = -1;
    int highestLine = -1;
    for (int i = 0; i < count; i++) {
        long bci = lntab[i].getStartBCI();
        int lineNumber = lntab[i].getLineNumber();

        /*
         * Some compilers will point multiple consecutive
         * lines at the same location. We need to choose
         * one of them so that we can consistently map back
         * and forth between line and location. So we choose
         * to record only the last line entry at a particular
         * location.
         */
        if ((i + 1 == count) || (bci != lntab[i+1].getStartBCI())) {
            // Remember the largest/smallest line number
            if (lineNumber > highestLine) {
                highestLine = lineNumber;
            }
            if ((lineNumber < lowestLine) || (lowestLine == -1)) {
                lowestLine = lineNumber;
            }
            LocationImpl loc =
                new LocationImpl(virtualMachine(), this, bci);
            loc.addBaseLineInfo(
                new BaseLineInfo(lineNumber, declaringType));

            // Add to the location list
            lineLocations.add(loc);

            // Add to the line -> locations map
            Integer key = new Integer(lineNumber);
            List mappedLocs = (List)lineMapper.get(key);
            if (mappedLocs == null) {
                mappedLocs = new ArrayList(1);
                lineMapper.put(key, mappedLocs);
            }
            mappedLocs.add(loc);
        }
    }

    info = new SoftLocationXRefs(SDE.BASE_STRATUM_NAME,
                            lineMapper, lineLocations,
                            lowestLine, highestLine);
    softBaseLocationXRefsRef = new SoftReference(info);
    return info;
}