字符串04——如何查看源码

1. 如何查看源码

如图选中一个next然后快捷键Ctrl+B可以看到源码

    public String next() {
        ensureOpen();
        clearCaches();
        modCount++;
        while (true) {
            String token = getCompleteTokenInBuffer(null);
            if (token != null) {
                matchValid = true;
                skipped = false;
                return token;
            }
            if (needInput)
                readInput();
            else
                throwFor();
        }
    }

可以非常容易的看出来，这个是由这个getCompleteTokenInBuffer方法实现的

然后我么继续看这个

    private String getCompleteTokenInBuffer(Pattern pattern) {
        matchValid = false;
        // Skip delims first
        matcher.usePattern(delimPattern);
        if (!skipped) { // Enforcing only one skip of leading delims
            matcher.region(position, buf.limit());
            if (matcher.lookingAt()) {
                // If more input could extend the delimiters then we must wait
                // for more input
                if (matcher.hitEnd() && !sourceClosed) {
                    needInput = true;
                    return null;
                }
                // The delims were whole and the matcher should skip them
                skipped = true;
                position = matcher.end();
            }
        }

        // If we are sitting at the end, no more tokens in buffer
        if (position == buf.limit()) {
            if (sourceClosed)
                return null;
            needInput = true;
            return null;
        }
        // Must look for next delims. Simply attempting to match the
        // pattern at this point may find a match but it might not be
        // the first longest match because of missing input, or it might
        // match a partial token instead of the whole thing.

        // Then look for next delims
        matcher.region(position, buf.limit());
        boolean foundNextDelim = matcher.find();
        if (foundNextDelim && (matcher.end() == position)) {
            // Zero length delimiter match; we should find the next one
            // using the automatic advance past a zero length match;
            // Otherwise we have just found the same one we just skipped
            foundNextDelim = matcher.find();
        }
        if (foundNextDelim) {
            // In the rare case that more input could cause the match
            // to be lost and there is more input coming we must wait
            // for more input. Note that hitting the end is okay as long
            // as the match cannot go away. It is the beginning of the
            // next delims we want to be sure about, we don't care if
            // they potentially extend further.
            if (matcher.requireEnd() && !sourceClosed) {
                needInput = true;
                return null;
            }
            int tokenEnd = matcher.start();
            // There is a complete token.
            if (pattern == null) {
                // Must continue with match to provide valid MatchResult
                pattern = FIND_ANY_PATTERN;
            }
            //  Attempt to match against the desired pattern
            matcher.usePattern(pattern);
            matcher.region(position, tokenEnd);
            if (matcher.matches()) {
                String s = matcher.group();
                position = matcher.end();
                return s;
            } else { // Complete token but it does not match
                return null;
            }
        }

        // If we can't find the next delims but no more input is coming,
        // then we can treat the remainder as a whole token
        if (sourceClosed) {
            if (pattern == null) {
                // Must continue with match to provide valid MatchResult
                pattern = FIND_ANY_PATTERN;
            }
            // Last token; Match the pattern here or throw
            matcher.usePattern(pattern);
            matcher.region(position, buf.limit());
            if (matcher.matches()) {
                String s = matcher.group();
                position = matcher.end();
                return s;
            }
            // Last piece does not match
            return null;
        }

        // There is a partial token in the buffer; must read more
        // to complete it
        needInput = true;
        return null;
    }

由于太多了，只看着几个个，会看就行了，还是应该要有一点点的英语基础