HDPCD-Java-复习笔记（10）-lab

不念不忘少年蓝@ 2022-06-07 07:49 123阅读 0赞

**Java lab booklet**

**Computing the Moving Average of a Stock**

**仅展示部分代码，其余参考前一个复习笔记。**

Reducer recycle logic's data example

window size:3, Symbol:Apple, Values:1.26, 3, 4

Apple \[1.26\]

Apple \[1.26, 3\], Apple \[3\]

Apple \[1.26, 3, 4\], Apple \[3,4\], Apple \[4\]

public static class MovingAverageReducer extends
    			Reducer<Stock, DoubleWritable, Text, DoubleWritable> {
    		private Text outputKey = new Text();
    		private DoubleWritable outputValue = new DoubleWritable();
    		private static final int WINDOW_SIZE = 50;
    		private LinkedList<StockWindow> windows = new LinkedList<StockWindow>();
    
    		@Override
    		protected void reduce(Stock key, Iterable<DoubleWritable> values,
    				Context context) throws IOException, InterruptedException {
    			StockWindow stockWindow;
    			for (DoubleWritable value : values) {
    				windows.add(new StockWindow(key.getSymbol()));
    				for (StockWindow window : windows) {
    					window.addPrice(value.get(), key.getDate());
    				}
    				if (windows.size() >= WINDOW_SIZE) {
    					stockWindow = windows.removeFirst();
    					outputKey.set(stockWindow.toString());
    					outputValue.set(stockWindow.getAverage());
    					context.write(outputKey, outputValue);
    				}
    			}
    			windows.clear();
    
    		}
    	}

package average;
    
    import java.util.LinkedList;
    
    public class StockWindow {
    	private String symbol;
    	private String endDate;
    	private LinkedList<Double> prices = new LinkedList<Double>();
    	
    
    	public StockWindow(String symbol) {
    		super();
    		this.symbol = symbol;
    	}
    
    	public String getSymbol() {
    		return symbol;
    	}
    
    	public String getEndDate() {
    		return endDate;
    	}
    
    	public void addPrice(double price, String endDate) {
    		prices.add(price);
    		this.endDate = endDate;
    	}
    	
    	public double getAverage() {
    		double sum = 0.0;
    		int count = 0;
    		for(double price: prices) {
    			count++;
    			sum += price;
    		}
    		return sum/count;
    	}
    	
    	public String toString() {
    		return symbol + "," + endDate;
    	}
    }