Practical sample (Java 8+) for `Runtime.exec` and output returning.

Exec.java

package template;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.concurrent.TimeUnit;
import java.util.stream.Collectors;
import lombok.NonNull;
import lombok.SneakyThrows;
import lombok.experimental.UtilityClass;
import lombok.val;

@UtilityClass
class Exec {

  @SneakyThrows
  static String exec(final @NonNull String cmd) {
    val pr = Runtime.getRuntime().exec(cmd);
    pr.waitFor(3, TimeUnit.SECONDS);
    val out = new BufferedReader(new InputStreamReader(pr.getInputStream(),
                                                       StandardCharsets.UTF_8));
    return out.lines().collect(Collectors.joining());
  }
}