curly-braces | 易学教程

Curly braces in “new” expression? (e.g. “new MyClass() { … }”)

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问题 What do the curly braces do there ? handler1 = new Handler() { public void handleMessage() { } }; object = new Class_Name() {}; ? This syntax exists only on Android or Java also? And what is it called in Java? Thank for your helps. 回答1: This is the syntax for creating an instance of anonymous class that extends Handler . This is part of Java. 回答2: This is happned when you create the instance reference of the Interface. For example I want to create the instance of the interface Runnable with

Do you use curly braces for additional scoping? [closed]

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问题 I mean other than using it when required for functions, classes, if, while, switch, try-catch. I didn\'t know that it could be done like this until I saw this SO question. In the above link, Eli mentioned that \"They use it to fold up their code in logical sections that don\'t fall into a function, class, loop, etc. that would usually be folded up.\" What other uses are there besides those mentioned? Is it a good idea to use curly braces to limit the scope of your variables and expand the

What's the purpose of using braces (i.e. {}) for a single-line if or loop?

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问题 I\'m reading some lecture notes of my C++ lecturer and he wrote the following: Use Indentation // OK Never rely on operator precedence - Always use parentheses // OK Always use a { } block - even for a single line // not OK , why ??? Const object on left side of comparison // OK Use unsigned for variables that are >= 0 // nice trick Set Pointer to NULL after deletion - Double delete protection // not bad The 3rd technique is not clear to me: what would I gain by placing one line in a { ... }

PHP - If/else, for, foreach, while - without curly braces?

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问题 Something that really would like to know but never found out are shortcuts in PHP. I am currently coding a function with a foreach loop with just a single statement inside. I tried to omit the curly braces as you can do in if/else control structures and it works. No errors. foreach($var as $value) $arr[] = $value; Now I tried to use it the same way but putting an if/else block inside it. Again, working and no errors. foreach($var as $value) if(1 + 1 == 2) { $arr[] = $value; }; Then, I thought

What do curly braces in Java mean by themselves?

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问题 I have some Java code that uses curly braces in two ways // Curly braces attached to an \'if\' statement: if(node.getId() != null) { node.getId().apply(this); } // Curly braces by themselves: { List<PExp> copy = new ArrayList<PExp>(node.getArgs()); for(PExp e : copy) { e.apply(this); } } outAMethodExp(node); What do those stand-alone curly braces after the first if statement mean? 回答1: The only purpose of the extra braces is to provide scope-limit. The List<PExp> copy will only exist within

Error: 'else' without 'if'

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Getting an else without if statement: import java.util.Scanner; public class LazyDaysCamp { public static void main (String[] args) { int temp; Scanner scan = new Scanner(System.in); System.out.println ("What's the current temperature?"); temp = scan.nextInt(); if (temp > 95 || temp < 20); System.out.println ("Visit our shops"); else if (temp <= 95) if (temp >= 80) System.out.println ("Swimming"); else if (temp >=60) if (temp <= 80) System.out.println ("Tennis"); else if (temp >= 40) if (temp < 60) System.out.println ("Golf"); else if (temp < 40) if (temp >= 20) System.out.println ("Skiing");

Why enclose blocks of C code in curly braces?

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问题 I am looking at some C code, and have noticed it is full of these curly braces surrounding blocks of code without any sort of control structure. Take a look-see: //do some stuff . . . fprintf(stderr, \"%.2f sec\\n\", (float)(clock() - t) / CLOCKS_PER_SEC); { //a block! why not? char *tmp_argv[3]; tmp_argv[0] = argv[0]; tmp_argv[1] = str; tmp_argv[2] = prefix; t = clock(); fprintf(stderr, \"[bwa_index] Convert nucleotide PAC to color PAC... \"); bwa_pac2cspac(3, tmp_argv); fprintf(stderr, \"%

PHP curly brace syntax for member variable

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问题 First question on SO and it\'s a real RTM candidate. But I promise you I\'ve looked and can\'t seem to find it. I\'ll happily do a #headpalm when it turns out to be a simple thing that I missed. Trying to figure out Zend Framework and came across the following syntax: $this->_session->{\'user_id\'} I have never seen the curly braces syntax used to access what appears to be a member variable. How is it different than $this->_session->user_id I\'m assuming that the _session is irrelevant, but

Curly Brackets in Arrow Functions

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问题 can someone, please explain the following: I\'m following Dan Abramov\'s lectures & doing the exercises. The code works fine, however, the tests fail when the following particular function is written with curly brackets **{ }** . case \'toggleTodo\' : return ( state.map( (one) => { oneTodo( one, action ) }) ); The same code works fine without curly brackets. case \'toggleTodo\' : return ( state.map( (one) => oneTodo( one, action ) ) ); Here is the JsBin. Please refer to line 31 onwards. 回答1:

Is there a difference in removing the curly braces from If statements in java

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问题 While watching thenewbostons tutorial on basic java, he teaches us to do if statements like this.(Notice the curly Braces) if(\"pie\"== \"pie\"){ System.out.println(\"Hurrah!\"); } So I tried removing the curly braces if(\"pie\"== \"pie\") System.out.println(\"Hurrah!\"); And it still works! Since I\'m new to java, I don\'t know why that works. And I want to know if removing(or adding) the curly braces give any benefits/disadvantages. 回答1: For a single statement it will remain same, but if