what is Ljava.lang.String;@

I have a string array selectCancel with setter and getter methods, which is a checkbox in my form. I am trying to get the checked values and I am getting the above result when I print.

I tried the Arrays.toString() method but it still prints the same.

I then did the following:

String checked = Arrays.toString(Employee.getSelectCancel());

I also tried with the Arrays.asList() and Arrays.copyOf()

So, how do I read this string?

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最佳答案

The method works if you provide an array. The output of

String[] helloWorld = {"Hello", "World"};
System.out.println(helloWorld);
System.out.println(Arrays.toString(helloWorld));

is

[Ljava.lang.String;@45a877
[Hello, World]

(the number after @ is almost always different)

Please tell us the return type of Employee.getSelectCancel()

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Ljava.lang.String;@ is returned where you used string arrays as strings. Employee.getSelectCancel() does not seem to return a String[]

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I also met this problem when I've made ListView for android app:

Map<String, Object> m;


for(int i=0; i < dates.length; i++){
m = new HashMap<String, Object>();
m.put(ATTR_DATES, dates[i]);
m.put(ATTR_SQUATS, squats[i]);
m.put(ATTR_BP, benchpress[i]);
m.put(ATTR_ROW, row[i]);
data.add(m);
}

The problem was that I've forgotten to use the [i] index inside the loop

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According to the Java Virtual Machine Specification (Java SE 8), JVM §4.3.2. Field Descriptors:

FieldType term | Type      | Interpretation
-------------- | --------- | --------------
L ClassName ;  | reference | an instance of class ClassName
[              | reference | one array dimension
...            | ...       | ...

the expression [Ljava.lang.String;@45a877 means this is an array ( [ ) of class java.lang.String ( Ljava.lang.String; ). And @45a877 is the address where the String object is stored in memory.

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[ stands for single dimension array
Ljava.lang.String stands for the string class (L followed by class/interface name)

Few Examples:

  1. Class.forName("[D") -> Array of primitive double
  2. Class.forName("[[Ljava.lang.String") -> Two dimensional array of strings.

List of notations:
Element Type : Notation
boolean : Z
byte : B
char : C
class or interface : Lclassname
double : D
float : F
int : I
long : J
short : S

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I have the same trouble: I make my own methods: So if I gonna call method like this:

Show("Additional String like this:"+ MyArray);//wrong command

have error! It's must be without "Additional String like this:" just do like this:

Show(AnyArray);//right command

package j;


class J{
public static String [] AnyArray = new String[3];


public static void main(String[] args) {


AnyArray[0]="String_0";
AnyArray[1]="String_1";
AnyArray[2]="String_2";


/******************************************************/
Show(AnyArray); //right
/*****************************************************/
Show("Additional String like this"+AnyArray);//wrong
/****************************************************/
}




public static void Show(String[] MyArray)
{
for(int i=0;i<=MyArray.length-1;i++){
System.out.println("MyArray ["+i+"]: "+MyArray[i]+"");
}
}






public static void Show(String MyString)
{
System.out.println(MyString);
}


}

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