初心者向けJava8ラムダ演習1 解答例 ref: http://qiita.com/aya_eiya/items/99ec41b1a49549017bd0

Practice1ASol.java

import java.util.stream.Stream;

public class Practice1ASol {
  static public void main(String[] args) {
    Stream.of("Hello", " ", "World", "!").forEach(System.out::print);
  }
}

Practice1Sol.java

import java.util.List;
import java.util.ArrayList;

public class Practice1Sol {
  static public void main(String[] args) {
    List<String> helloWorld = new ArrayList<String>(3);
    helloWorld.add("Hello");
    helloWorld.add(" ");
    helloWorld.add("World");
    helloWorld.add("!");
    helloWorld.stream().forEach(s -> {
      System.out.print(s);
    });
  }
}

Practice2ASol.java

import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.List;
import java.util.Map.Entry;

public class Practice2ASol {
  static private final int MAX = 1024;

  static public void main(String[] args) {
    String sourceText = "this is an test script to read.";
    List<Integer> sumBox = new ArrayList<>(sourceText.length());
    sourceText
      .chars()
      .mapToObj(c->{
        sumBox.add(sumBox.size() == 0 ? c : c + sumBox.get(sumBox.size() - 1) );
        return new AbstractMap.SimpleEntry<>(sumBox.get( sumBox.size()-1),c);
      })
      .filter(ent->ent.getKey()<=MAX)
      .mapToInt(Entry::getValue)
      .map(c -> c > 'm' ? Character.toUpperCase(c) : c)
      .forEach(c -> System.out.print((char) c));
    System.out.print("\n");
    if (sumBox.get(sumBox.size() - 1) > MAX) {
      System.out.println("script stopped for MAX size limitation.");
    }
  }
}

Practice2Sol.java

public class Practice2Sol {
  static public void main(String[] args) {
    String sourceText = "this is an test script to read.";
    sourceText
      .chars()
      .limit(sourceText.indexOf('.'))
      .map(c -> c > 'm' ? Character.toUpperCase(c) : c)
      .forEach(c -> System.out.print((char) c));
    System.out.print(".\n");
  }
}