英文:
Map.compute function in java
问题
import java.util.*;
public class JavaApplication32 {
public static void main(String args[]) {
HashMap<String, String> map = new HashMap<>();
map.put("Name", "Aman");
map.put("Address", "Kolkata");
map.compute("Name", (key, val) -> (val == null) ? "Gaurav" : val = "Great");
System.out.println(map.get("Name"));
}
}
上述代码出现错误。但是当值的数据类型选择为 int 时，代码可以正常工作。
英文:
import java.util.*;
public class JavaApplication32 {
public static void main(String args[]) {
HashMap<String, String> map = new HashMap<>();
map.put("Name", "Aman");
map.put("Address", "Kolkata");
map.compute("Name", (key, val) -> (val == null) ? "Gaurav" : val = "Great");
System.out.println(map.get("Name"));
}
}
The above code shows an error. But when the value data type is chosen as int, the code works.
答案1
得分: 0
不需要分配 `val`
import java.util.*;
public class JavaApplication32 {
public static void main(String args[])
{
HashMap<String, String> map = new HashMap<>();
map.put("Name", "Aman");
map.put("Address", "Kolkata");
map.compute("Name", (key, val) -> (val==null) ? "Gaurav" : "Great");
System.out.println(map.get("Name"));
}
}
英文:
There is no need to assign val
import java.util.*;
public class JavaApplication32 {
public static void main(String args[])
{
HashMap<String, String> map = new HashMap<>();
map.put("Name", "Aman");
map.put("Address", "Kolkata");
map.compute("Name", (key, val) -> ( val==null) ? "Gaurav" : "Great");
System.out.println(map.get("Name"));
}
}
答案2
得分: 0
替换
map.compute("Name", (key, val) -> (val == null) ? "Gaurav" : val = "Great");
为
map.compute("Name", (key, val) -> (val == null) ? "Gaurav" : "Great");
输出:
Great
解释:
三元操作符的语法如下:
变量 = 条件 ? 如果条件为真的值 : 如果条件为假的值
例如，下面的代码将x的值赋给z:
int x = 10, y = 5, z;
z = x > y ? x : y;
System.out.println(z);
然而，如果您想在语句中保留左操作数，您可以使用()，如下所示:
map.compute("Name", (key, val) -> (val == null) ? "Gaurav" : (val = "Great"));
类似地，
z = x > y ? x : (z = y);
尽管上面给出的这两个语句可以成功编译，但我建议您不要这样做，因为这会让阅读您代码的人感到困惑。
英文:
Replace
map.compute("Name", (key, val) -> ( val==null) ? "Gaurav" : val="Great");
with
map.compute("Name", (key, val) -> (val == null) ? "Gaurav" : "Great");
Output:
Great
Explanation:
The syntax of ternary operator is as follows:
variable = condition ? value-if-condition-is-true : value-if-condition-is-false
e.g. the following code assigns the value of x into z
int x = 10, y = 5, z;
z = x > y ? x : y;
System.out.println(z);
However, if at all you want to keep the left operand inside the statement, you can do it using () as follows:
map.compute("Name", (key, val) -> (val == null) ? "Gaurav" : (val = "Great"));
Similarly,
z = x > y ? x : (z = y);
Even though these two statements given above will be compiled successfully, I recommend you never do it like this as it will simply confuse anyone going through your code.
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