Java interview (5)

10 Java programming experiences are listed here

1 string constants are placed in front

The string constant is placed on the left side of the Equals () comparison item to prevent accidental nullpointerexception.

//  Bad if (Variable.equals ("literal"//  goodif ("literal". Equals (variable)) {...}

2 Don't believe-1

//  Bad if (String.IndexOf (character)! =-1) {...} // Good if (String.IndexOf (character) >= 0) { ... }

3 Avoidance of accidental assignment

If there is a constant in your expression, place it on the left side of the equation. So when you're going to add another =, it's not easy to go wrong.

// Ooops if (variable = 5//  Better (because causes an error)if (5 = variable) {...} // Intent (remember. Paranoid JavaScript: = = =)if (5 = = = variable) {...}

4 checking for null and length

Whenever you have a collection, an array, or something else, make sure it exists and is not empty

//  Bad if (Array.Length > 0) {...} // Good if null && array.length > 0) {...}

Of course, you can also use Collections.isempty () to judge

5 All methods are declared with final

You can tell me any opening and closing principle you want, but that's nonsense. I don't believe you (can inherit my class correctly), nor do I trust myself (not accidentally inheriting my class). So all but the interface (specifically for inheritance) should be strictly final

//  Bad  Public void  //  good. Don ' t touch.  Public Final void Donttouch () {...}

6 All variables and parameters are declared with final

//  Bad void input (String importantmessage) {    = "...";      = Importantmessage = "LOL accident"//  goodfinalvoid input (  Final  string importantmessage) {    final string answer = "...";}

7 overload don't believe in generics

// Bad<T>voidBad (T value) {Bad (collections.singletonlist (value));}<T>voidBad (list<t>values) {    ...} //GoodFinal<T>voidGood (FinalT value) {    if(Valueinstanceoflist) Good ((list<?>) value); ElseGood (collections.singletonlist (value));} Final<T>voidGood (FinalList<t>values) {    ...}

8 always add default to the switch statement

// BadSwitch(value) { Case1:foo (); Break;  Case2:bar (); Break;} //GoodSwitch(value) { Case1:foo (); Break;  Case2:bar (); Break; default:        Throw NewThreaddeath ("that ' ll teach them");}

9 Use curly braces to separate each case block of a switch

//Bad , doesn ' t compileSwitch(value) { Case1:intj = 1; Break;  Case2:intj = 2; Break; J Repeating Definition}//GoodSwitch(value) { Case1: {        Final intj = 1;  Break; }     Case2: {        Final intj = 2;  Break; }     //Remember:    default:         Throw NewThreaddeath ("that ' ll teach them");}

Java interview (5)