LeoHeo

@Documented
@Retention(RetentionPolicy.CLASS) // default CLASS -> SOURCE, RUNTIME으로 변경할 필요 없음
@Target(ElementType.METHOD)
public @interface PerformaceLogging {
}

LeoHeo

long begin = Sytem.currentTimeMillis();

// do something....
// 기존코드

System.out.println(Sytem.currentTimeMillis() - begin);

LeoHeo

axios.get(url, {
    responseType: 'arraybuffer'
}).then(function (response) {
    var blob = new Blob([response.data], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' });
    var blobURL = window.URL.createObjectURL(blob);
    var tempLink = document.createElement('a');
    tempLink.style.display = 'none';
    tempLink.href = blobURL;
    tempLink.setAttribute('download', 'test.xlsx');
    document.body.appendChild(tempLink);

LeoHeo

  @Override
  public int hashCode() {
    return Objects.hash(getId());
  }

LeoHeo

public V put(K key, V value) {
    return putVal(hash(key), key, value, false, true);
}

static final int hash(Object key) {
    int h;
    return (key == null) ? 0 : (h = key.hashCode()) ^ (h >>> 16);
}

LeoHeo

public class HashSet<E>
    extends AbstractSet<E>
    implements Set<E>, Cloneable, java.io.Serializable
{
     private transient HashMap<E,Object> map;
    
    /**
     * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
     * default initial capacity (16) and load factor (0.75).
     */

LeoHeo

Set<Student> studentSet = new HashSet<>();
studentSet.add(leo1);
studentSet.add(new Student(1L, "Leo"));

System.out.println("studentSet size => " + studentSet.size()); // studentSet size => 2

LeoHeo

List<Student> students = new ArrayList<>();
students.add(leo1);
System.out.println("students contains Leo => " + students.contains(new Student(1L, "Leo"))); // true

LeoHeo

@Override
public boolean equals(Object o) {
  if (this == o) {
    return true;
  }
  if (!(o instanceof Student)) {
    return false;
  }
  Student student = (Student) o;
  return Objects.equals(getId(), student.getId()); // Java7+ 부터 사용할 수 있는 `Objects.equals`를 사용해봤다.

LeoHeo

package io.github.leoheo.equals;

/**
 * @author Heo, Jin Han
 * @since 2018-06-10
 */
public class Student {

  private Long id;
  private String name;