回答編集履歴
2
java.util.stream.Streamに訂正
test
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@@ -32,7 +32,7 @@
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**java.util.Streamを使用する統計処理(追記)**
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**java.util.stream.Streamを使用する統計処理(追記)**
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java.util.Streamを使用する例を追記
test
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@@ -28,4 +28,114 @@
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```
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`""`の代わりに奪三振率の高い`"Yu Darvish"` としたいですね。
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`""`の代わりに奪三振率の高い`"Yu Darvish"` としたいですね。（文字列リテラルなら何でもよい）
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**java.util.Streamを使用する統計処理(追記)**
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バッターの打率を集計する専用クラス。Streamを使用して作り直したソースを追記します。
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```Java
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import java.io.BufferedReader;
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import java.io.FileReader;
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import java.io.IOException;
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import java.io.PrintStream;
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import java.util.Map;
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import java.util.TreeMap;
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import java.util.AbstractMap.SimpleEntry;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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public class EvaConv2 {
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public static void main(String[] args) {
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try {
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PlayerMatrix.read("ファイル名.EVA").writeTo(System.out);
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} catch (IOException e) {
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e.printStackTrace();
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}
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}
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private static class PlayerMatrix {
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private final Map<String, Double> freqs;
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public PlayerMatrix(Stream<String> lines) throws IOException {
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freqs = lines.map(
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line -> {String[] t = line.split(","); return new SimpleEntry<>(t[3], t[16]);
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}).collect(
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Collectors.groupingBy(
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SimpleEntry::getKey,
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TreeMap::new,
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Collectors.averagingDouble(e -> Double.valueOf(e.getValue()))
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));
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}
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void writeTo(PrintStream out) {
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out.println("player,batting average (BA)");
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freqs.entrySet().forEach(e -> out.printf("%s,%1.3f\n", e.getKey(), e.getValue()));
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}
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static PlayerMatrix read(String filename) throws IOException {
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PlayerMatrix matrix = null;
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try (BufferedReader br = new BufferedReader(new FileReader(filename))) {
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matrix = new PlayerMatrix(br.lines());
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}
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return matrix;
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}
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}
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}
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```
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141
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たぶんこれより`R`で作る方が簡単でしょう。
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