Technical Indicators

Technical indicators (a.k.a. technicals) transform price/volume data into structured signals that power rules and strategies. ta4j ships with 130+ indicators covering every major category plus building blocks for your own creations.

Category	Highlights	Docs
Trend / Moving Averages	SMA, EMA, HMA, VIDYA, Jurik, Displaced variants, SuperTrend, Renko helpers.	Moving Average Indicators
Momentum & Oscillators	RSI family, NetMomentum (new), MACD/MACDV, KST, Stochastics, Calm (CMO), ROC.	This page
Volatility & Bands	ATR, Donchian, Bollinger, Keltner, Average True Range trailing stops.	Bar Series & Bars (for ATR-based stops)
Volume & Breadth	OBV, VWAP/VWMA, Accumulation/Distribution, Chaikin, Volume spikes.	Indicators package
Candle/Pattern	Hammer, Shooting Star, Three White Soldiers, DownTrend/UpTrend.	indicators.candles
Price Transformations	RenkoUp/Down/X (0.19), Heikin Ashi builders, BinaryOperationIndicator/UnaryOperationIndicator transforms.	indicators.renko

Browse org.ta4j.core.indicators in your IDE for the full list—packages mirror the table above.

Composition example

ClosePriceIndicator close = new ClosePriceIndicator(series);
SMAIndicator fast = new SMAIndicator(close, 9);
SMAIndicator slow = new SMAIndicator(close, 50);
MACDVIndicator macdv = new MACDVIndicator(series, 12, 26, 9);
NetMomentumIndicator netMomentum = new NetMomentumIndicator(series, 14);

Indicator<Num> trendBias = BinaryOperationIndicator.division(fast, slow);
Indicator<Num> blendedMomentum = BinaryOperationIndicator.add(macdv.getMacd(), netMomentum);

• BinaryOperationIndicator / UnaryOperationIndicator replace the older TransformIndicator/CombineIndicator classes (removed in 0.19).
• Output indicators can feed directly into rules (new OverIndicatorRule(trendBias, numOf(1.0))) or become inputs to other indicators.

Backtesting indicators

Indicators should be evaluated the same way strategies are—prefer realistic data with survivorship-bias filters. The Usage Examples page links to CSV/Chart demos where indicators are plotted alongside price bars.

Caching & stability

• Every indicator extends CachedIndicator, so once a value is computed (except for the most recent bar) it is reused.
• Mutating the latest bar (common with streaming data) invalidates just that slot; the rest stays cached.
• Use indicator.getCountOfUnstableBars() / indicator.isStable(index) to understand when the values become reliable (and pass that number to strategy.setUnstableBars(...)).
• When using moving BarSeries via setMaximumBarCount, cached entries older than the oldest remaining bar disappear. Always guard against NaN if you try to access evicted indexes.

Creating custom indicators

Sub-class CachedIndicator<Num> or compose existing indicators with operations. Guidelines:

• Accept dependencies via constructor injections (Indicator<Num> base) rather than pulling directly from a BarSeries.
• Respect the Num abstraction: use Num arithmetic (plus, minus, etc.) and produce values via the series NumFactory.
• Override getUnstableBars() / isStable() when your indicator requires warm-up bars (e.g., multi-stage EMAs).
• If you need state across indices, store it in the indicator (ta4j handles thread safety by design if you limit state to the calculation path).

Tips

• Normalize values when mixing indicators with different ranges (e.g., convert RSI to 0–1 before feeding it into a vote rule with MACD).
• When working with unconventional chart types (Renko, Heikin Ashi), prefer the dedicated builders/indicators shipped in 0.18/0.19—they keep the math consistent across strategies.
• Combine price- and volume-driven indicators to reduce false positives (e.g., new AndIndicatorRule(new OverIndicatorRule(macdv, zero), new OverIndicatorRule(vwma, close))).
• Document indicator usage inside strategies so others know the intent—especially if the indicator is non-standard or parameter-sensitive. Technicals also need to be backtested on historic data to see how effective they would have been to predict future prices. Some examples are available in this sense.

Visualizing indicators

You can visualize indicators on charts using the ChartBuilder API. Indicators can be displayed as overlays on price charts or as separate sub-charts:

ClosePriceIndicator closePrice = new ClosePriceIndicator(series);
SMAIndicator sma = new SMAIndicator(closePrice, 50);

ChartWorkflow chartWorkflow = new ChartWorkflow();
chartWorkflow.builder()
    .withSeries(series)
    .withIndicatorOverlay(sma)
    .withLineColor(Color.ORANGE)
    .display();

Caching mechanism

Some indicators need recursive calls and/or values from the previous bars in order to calculate their last value. For that reason, a caching mechanism has been implemented for all the indicators provided by ta4j. This system avoids calculating the same value twice. Therefore, if a value has been already calculated it is retrieved from cache the next time it is requested. Values for the last Bar will not be cached. This allows you to modify the last bar of the BarSeries by adding price/trades to it and to recalculate results with indicators.

Warning! If a maximum bar count has been set for the related bar Series, then the results calculated for evicted bars are evicted too. They also cannot be recomputed since the related bars have been removed. That being said, moving bar Series should not be used when you need to access long-term past bars.