返回值的三元运算符 - Java/Android
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Ternary operator to return value- Java/Android
提问by sumit
Just switched to Java from php
刚从php切换到Java
I encountered following issue
我遇到了以下问题
I want to rewrite
我想重写
if(usrname.equals(username) && (passwd.equals(password))){
return true;
}
else{
return false;
}
as
作为
(usrname.equals(username) && passwd.equals(password) )? return true : return false;
it is not working(syntax error) however,
但是，它不起作用（语法错误），
int a=1;
int b=2;
int minVal = a < b ? a : b;
is working
正在工作
Why ternary operator are not behaving correctly while returning value depending on some condition
为什么三元运算符在根据某些条件返回值时行为不正确
EDIT
编辑
return (usrname.equals(username) && passwd.equals(password));
could be solution if it return boolean .
如果它返回 boolean 可能是解决方案。
lets say i need
可以说我需要
(usrname.equals(username) && passwd.equals(password) )? return "member": return "guest";
采纳答案by Aniket Thakur
You can do
你可以做
return (usrname.equals(username) && passwd.equals(password) )? true : false;
trueand falsecan be replaced by any return value you want. If it is just boolean then you can avoid ternary operator altogether. Just do
true并且false可以替换为您想要的任何返回值。如果它只是布尔值，那么您可以完全避免使用三元运算符。做就是了
return (usrname.equals(username) && passwd.equals(password));
回答by Ruchira Gayan Ranaweera
Why redundant boolean
为什么冗余 boolean
Just use
只需使用
return (usrname.equals(username) && passwd.equals(password));
回答by Troncador
By the way you can simplify:
顺便说一下，您可以简化：
return (usrname.equals(username) && passwd.equals(password) )? return true : return false;
返回 (usrname.equals(username) && passwd.equals(password) )？返回真：返回假；
To:
到：
return usrname.equals(username) && passwd.equals(password);
返回 usrname.equals(username) && passwd.equals(password);
The ternary operator work similar in php than Java, I think you have made a silly mistake, maybe "username" have a space or another white character
三元运算符在 php 中的工作方式与 Java 相似，我认为您犯了一个愚蠢的错误，也许“用户名”有一个空格或另一个白色字符
String a1 = "a";
String b1 = "b";
String a2 = "a";
String b2 = "b";
System.out.println((a1.equals(a2)&&b1.equals(b2))?"true":"false");
it return "true"
它返回“真”
回答by Stephen C
lets say I need
(usrname.equals(u) && passwd.equals(p)) ? return "member" : return guest";
可以说我需要
(usrname.equals(u) && passwd.equals(p)) ? return "member" : return guest";
The correct syntax is:
正确的语法是：
return (usrname.equals(u) && passwd.equals(p)) ? "member" : "guest";
The general form of the ternary operator is
三元运算符的一般形式是
expression-1 ? expression-2 : expression-3
where expression-1has type boolean, and expression-2and expression-3have the same type1.
其中expression-1具有类型boolean，并且expression-2和expression-3具有相同的类型1。
In your code, you were using returnstatements where expressions are required. In Java, a returnstatement is NOT a valid expression.
在您的代码中，您使用了return需要表达式的语句。在 Java 中，return语句不是有效的表达式。
1 - This doesn't take account of the conversionsthat can take. For the full story, refer to the JLS.
1 - 这没有考虑可以进行的转换。有关完整故事，请参阅 JLS。
Having said that, the best way to write yourexample doesn't uses the conditional operator at all:
说了这么多，写的最好方法你例子并不用条件运算都：
return usrname.equals(username) && passwd.equals(password);
回答by Sameer Sinha
Java ternary operator is an expression, and is thus evaluated to a single value. As per the Javadocs, for below given expression
Java 三元运算符是一个表达式，因此被评估为单个值。根据Javadocs，对于下面给定的表达式
result = someCondition ? value1 : value2;
if the boolean condition is true then assign the value of value1to the result, else assign value2to the result. Both value1 and value2 should be of same value type.
如果布尔条件为真，则将value1的值分配给结果，否则将value2分配给结果。value1 和 value2 都应该是相同的值类型。
Hence the correct syntax of a return statement would be
因此 return 语句的正确语法是
return boolean_condition ? value_when_true : value_when_false
