Scala example source code file (MemoryHistory.java)

This example Scala source code file (MemoryHistory.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Scala tags/keywords

charsequence, charsequence, default_max_size, entriesiterator, entry, entry, entryimpl, entryimpl, history, linkedlist, listiterator, listiterator, nosuchelementexception, unsupportedoperationexception, util

The Scala MemoryHistory.java source code

/*
 * Copyright (c) 2002-2007, Marc Prud'hommeaux. All rights reserved.
 *
 * This software is distributable under the BSD license. See the terms of the
 * BSD license in the documentation provided with this software.
 */

package scala.tools.jline.console.history;

import java.util.Iterator;
import java.util.LinkedList;
import java.util.ListIterator;
import java.util.NoSuchElementException;

/**
 * Non-persistent {@link History}.
 *
 * @author <a href="mailto:mwp1@cornell.edu">Marc Prud'hommeaux
 * @author <a href="mailto:jason@planet57.com">Jason Dillon
 * @since 2.3
 */
public class MemoryHistory
    implements History
{
    public static final int DEFAULT_MAX_SIZE = 500;

    private final LinkedList<CharSequence> items = new LinkedList();

    private int maxSize = DEFAULT_MAX_SIZE;

    private boolean ignoreDuplicates = true;

    private boolean autoTrim = false;

    // NOTE: These are all ideas from looking at the Bash man page:

    // TODO: Add ignore space? (lines starting with a space are ignored)

    // TODO: Add ignore patterns?

    // TODO: Add history timestamp?

    // TODO: Add erase dups?

    private int offset = 0;

    private int index = 0;

    public void setMaxSize(final int maxSize) {
        this.maxSize = maxSize;
        maybeResize();
    }

    public int getMaxSize() {
        return maxSize;
    }

    public boolean isIgnoreDuplicates() {
        return ignoreDuplicates;
    }

    public void setIgnoreDuplicates(final boolean flag) {
        this.ignoreDuplicates = flag;
    }

    public boolean isAutoTrim() {
        return autoTrim;
    }

    public void setAutoTrim(final boolean flag) {
        this.autoTrim = flag;
    }

    public int size() {
        return items.size();
    }

    public boolean isEmpty() {
        return items.isEmpty();
    }

    public int index() {
        return offset + index;
    }

    public void clear() {
        items.clear();
        offset = 0;
        index = 0;
    }

    public CharSequence get(final int index) {
        return items.get(index - offset);
    }

    public void add(CharSequence item) {
        assert item != null;

        if (isAutoTrim()) {
            item = String.valueOf(item).trim();
        }

        if (isIgnoreDuplicates()) {
            if (!items.isEmpty() && item.equals(items.getLast())) {
                return;
            }
        }

        items.add(item);

        maybeResize();
    }

    public void replace(final CharSequence item) {
        items.removeLast();
        add(item);
    }

    private void maybeResize() {
        while (size() > getMaxSize()) {
            items.removeFirst();
            offset++;
        }

        index = size();
    }

    public ListIterator<Entry> entries(final int index) {
        return new EntriesIterator(index - offset);
    }

    public ListIterator<Entry> entries() {
        return entries(offset);
    }

    public Iterator<Entry> iterator() {
        return entries();    
    }

    private static class EntryImpl
        implements Entry
    {
        private final int index;

        private final CharSequence value;

        public EntryImpl(int index, CharSequence value) {
            this.index = index;
            this.value = value;
        }

        public int index() {
            return index;
        }

        public CharSequence value() {
            return value;
        }

        @Override
        public String toString() {
            return String.format("%d: %s", index, value);
        }
    }

    private class EntriesIterator
        implements ListIterator<Entry>
    {
        private final ListIterator<CharSequence> source;

        private EntriesIterator(final int index) {
            source = items.listIterator(index);
        }

        public Entry next() {
            if (!source.hasNext()) {
                throw new NoSuchElementException();
            }
            return new EntryImpl(offset + source.nextIndex(), source.next());
        }

        public Entry previous() {
            if (!source.hasPrevious()) {
                throw new NoSuchElementException();
            }
            return new EntryImpl(offset + source.previousIndex(), source.previous());
        }

        public int nextIndex() {
            return offset + source.nextIndex();
        }

        public int previousIndex() {
            return offset + source.previousIndex();
        }

        public boolean hasNext() {
            return source.hasNext();
        }

        public boolean hasPrevious() {
            return source.hasPrevious();
        }

        public void remove() {
            throw new UnsupportedOperationException();
        }

        public void set(final Entry entry) {
            throw new UnsupportedOperationException();
        }

        public void add(final Entry entry) {
            throw new UnsupportedOperationException();
        }
    }

    //
    // Navigation
    //

    /**
     * This moves the history to the last entry. This entry is one position
     * before the moveToEnd() position.
     *
     * @return Returns false if there were no history entries or the history
     *         index was already at the last entry.
     */
    public boolean moveToLast() {
        int lastEntry = size() - 1;
        if (lastEntry >= 0 && lastEntry != index) {
            index = size() - 1;
            return true;
        }

        return false;
    }

    /**
     * Move to the specified index in the history
     * @param index
     * @return
     */
    public boolean moveTo(int index) {
        index -= offset;
        if (index >= 0 && index < size() ) {
            this.index = index;
            return true;
        }
        return false;
    }

    /**
     * Moves the history index to the first entry.
     *
     * @return Return false if there are no entries in the history or if the
     *         history is already at the beginning.
     */
    public boolean moveToFirst() {
        if (size() > 0 && index != 0) {
            index = 0;
            return true;
        }

        return false;
    }

    /**
     * Move to the end of the history buffer. This will be a blank entry, after
     * all of the other entries.
     */
    public void moveToEnd() {
        index = size();
    }

    /**
     * Return the content of the current buffer.
     */
    public CharSequence current() {
        if (index >= size()) {
            return "";
        }

        return items.get(index);
    }

    /**
     * Move the pointer to the previous element in the buffer.
     *
     * @return true if we successfully went to the previous element
     */
    public boolean previous() {
        if (index <= 0) {
            return false;
        }

        index--;

        return true;
    }

    /**
     * Move the pointer to the next element in the buffer.
     *
     * @return true if we successfully went to the next element
     */
    public boolean next() {
        if (index >= size()) {
            return false;
        }

        index++;

        return true;
    }


}