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Code Suggestions

General#

  • Use as many lambda function expressions as possible.

  • Method parameters must be modified with final.

  • Constants modified static final must be named in upper case.

  • Methods should not have too many parameters.

  • Clear unused classes and methods.

  • Use linux line separators.

  • Tab size is 4 and keep indents on empty lines.

  • All code passage of Checkstyle: https://github.com/apache/shenyu/blob/master/script/shenyu_checkstyle.xml

  • When adding a new file, you need to add the apache protocol in the header of the file.

Object#

  • Use Optional transform Null.

Optional.ofNullable(xxx).orElse(obj)

  • Use Objects Judgment Null Or NotNull.

Objects.isNull(obj) OR Objects.nonNull(obj)

  • Use Objects.equals Judgment are they equal.

Objects.equals(obj1, obj2)

  • Creater objects outside of a for loop.
Object object = null;for () {    object = new Object();}

Collection#

  • must indicate initial capacity to avoid recalculate capacity.

List#

  • Use LinkedList when you need to add or delete elements, Else use ArrayList.

  • Use org.apache.commons.collections4.CollectionUtils Judgment Is empty Or Not empty.

CollectionUtils.isEmpty(list) or CollectionUtils.isNotEmpty(data)

Map#

  • Use ConcurrenHashMap when considering concurrency of threads, Else use HashMap.

  • Iterate over map using the most efficient way Or use lambda function.

Set<Map.Entry<String, String>> entrySet = map.entrySet();Iterator<Map.Entry<String, String>> iter = entrySet.iterator();while (iter.hasNext()) {        Map.Entry<String, String> entry = iter.next();      }

String#

  • Use org.apache.commons.lang3.StringUtils Judgment Is empty Or Not empty.

StringUtils.isEmpty(list) or StringUtils.isNotEmpty(data)

  • String.join should be used when string concatenation occurs.

String join(CharSequence delimiter, CharSequence... elements)

Exception#

  • Do not use try...catch in a loop, it should be on the outermost layer.
try {  for () {  }} catch () {  }
  • Do not use printStackTrace().

  • Please use custom exceptions or ShenyuException.

Resource#

  • Please use try with resource to close resource.

Several methods to judge and handle Null#

  • Judge self if Null or not, and also need to transform self, below are some representative examples:
    current : result.setXXX(null == a ? b.getXXX() : b.getXXX(a));
    recommendation : Optional.ofNullable(a).map(b::getXXX).orElse(b.getXXX());
    current : return null == a ? b.newC() : b.newC(a.getD(), a.getE());
    recommendation : return Optional.ofNullable(a).map(e -> b.newC(e.getD(),e.getE())).orElse(b.newC());
    current : return null == a.getB() ? null : a.getB().getC();
    recommendation : return Optional.ofNullable(a.getB()).map(C::getD).orElse(null);
    current : return null == a ? new B() : C.newD(a);
    recommendation : return Optional.ofNullable(a).map(B::newC).orElse(new D());

  • Directly compare current object with Null, below are some representative examples:
    current : public void xxx(Object o){if(null == o){retrun;}}
    current : public boolean wasNull() {return null == currentRow;}
    recommendation :Use JDK8's Objects.isNull method.

  • Judge self if Null or not, and also need to return self related ternary operator, below are some representative examples:
    current : this.a = null == a ? new B().newC() : a;
    recommendation : Optional.ofNullable(a).orElse(new B().newC());
    current : a = null == a ? b.getC().getD() : a;
    recommendation : a = Optional.ofNullable(a).orElse(b.getC().getD());
    current : return null == a.getB() ? c : a.getB();
    recommendation : return Optional.ofNullable(a.getB()).orElse(c);
    current :

    BigDecimal c;BigDecimal s;if (null == c) {  c = new BigDecimal("0");}if (null == s) {  s = new BigDecimal("0");}

    recommendation : c = Optional.ofNullable(c).orElse(new BigDecimal("0")); s = Optional.ofNullable(s).orElse(new BigDecimal("0"));
    current : return null == results.get(0) ? 0 : results.get(0);
    recommendation : return Optional.ofNullable(results.get(0)).orElse(0);
    current : return null == getA().getB() ? Collections.emptyList() : Collections.singletonList(getA().getB());
    recommendation : return Optional.ofNullable(getA().getB()).map(Collections::singletonList).orElse(Collections.emptyList());

  • Judge self if Null or not, and also need to return self independent ternary operator, below are some representative examples:
    current : A a = null == b ? cMap.values().iterator().next() : cMap.get(d);
    current : return null == a ? new B() : new B(c);
    recommendation : No modification.

  • Judge collection is null or not, below are some representative examples:
    current :

    private boolean isEmpty(final List<String> xxx) {    return null == xxx || xxx.isEmpty();}

    recommendation : Add a collection tool class to make unified judgment.

  • Judge Map's value is Null or not, below are some representative examples:
    current :

    public Collection<String> getA(final String b) {   Collection<String> result = cMap.get(b);   if (null == result) {      result = Collections.emptySet();   }   return result;}

    recommendation : Use Map.getOrDefault() method.

    public Collection<String> getA(final String b) {  return cMap.getOrDefault(b, Collections.emptySet());}
  • Judge is Null or not, if yes throw exception, else execute next step, below are some representative examples:
    current :

    private Collection<String> doXxx(final Collection<String> a, final Object<?> b) {  if (null == c) {     throw new Exception("XXX");  }  return c.doXxx(a,new Object(b.getXXX(), b.getXXX(), b.getXXX()));}

    recommendation :

    private Collection<String> doXxx(final Collection<String> a, final Object<?> b) {     return Optional.ofNullable(c).map(e -> e.doXxx(a,            new Object(b.getXXX(), b.getXXX(), b.getXXX())))           .orElseThrow(()-> new Exception("XXX"));}
  • Judge is Null or not, and return Optional wrapped object, below are some representative examples:
    current : return null == a ? Optional.empty() : Optional.ofNullable(a.getXXX());
    recommendation : return Optional.ofNullable(a).map(e -> e.getXXX());