Convert String to Staticstring

How to convert a String into a &'static str

Updated for Rust 1.0

You cannot obtain &'static str from a String because Strings may not live for the entire life of your program, and that's what &'static lifetime means. You can only get a slice parameterized by String own lifetime from it.

To go from a String to a slice &'a str you can use slicing syntax:

let s: String = "abcdefg".to_owned();
let s_slice: &str = &s[..];  // take a full slice of the string

Alternatively, you can use the fact that String implements Deref<Target=str> and perform an explicit reborrowing:

let s_slice: &str = &*s;  // s  : String 
                          // *s : str (via Deref<Target=str>)
                          // &*s: &str

There is even another way which allows for even more concise syntax but it can only be used if the compiler is able to determine the desired target type (e.g. in function arguments or explicitly typed variable bindings). It is called deref coercion and it allows using just & operator, and the compiler will automatically insert an appropriate amount of *s based on the context:

let s_slice: &str = &s;  // okay

fn take_name(name: &str) { ... }
take_name(&s);           // okay as well

let not_correct = &s;    // this will give &String, not &str,
                         // because the compiler does not know
                         // that you want a &str

Note that this pattern is not unique for String/&str - you can use it with every pair of types which are connected through Deref, for example, with CString/CStr and OsString/OsStr from std::ffi module or PathBuf/Path from std::path module.

Get/Set non-static String to static string to pass through Java

First thing first; I understand that it is not possible to call a static method from a non-static method

First things first, you can call a static method from a non-static method. You can't call a non-static method from a static method.

You can set a static variable from a non-static method if that is your intention:

static String foo;

void myNonStaticMethod() {
    foo = "bar";
}

Java, how to convert a string to class and call its static method?

To create new instance you need to do the following

Class c = Class.forName("Item");
Item i = (Item)c.newInstance();

If you want to invoke static method you just call it on class instead of instance

Item.test();

Or you can use reflection without directly reference to class

Class c = Class.forName("Item");
Method method = c.getMethod("test");
method.invoke(null);

How to replace a static string with a variable and convert to long?

Your text contains a trailing space. You should remove it by trim() method. Try the following code & it should work for you.

String macAddr = last_mac.getText().trim();

Convert String to Reverse String Using Recursion in Java

This solution might be helpful. The comments explain the code pretty much.

public static String reverse_recursion(String str) {
    String[] arry = str.split(" ", 2); //Split into a maximum of 2 Strings

    if (arry.length > 1) { //If there is more than 1 word in arry
        //Return the reverse of the rest of the str (arry[1])           
        //and concatenate together with the first word (arry[0])
        return reverse_recursion(arry[1]) + " " + arry[0];
    }

    return arry[0]; //If less than or equal to 1 word, just return that word
}

How to change static string value by another class?

ConnectionStringExcel is initialized using filename but it won't track future changes.

You can convert ConnectionStringExcel into a readonly property with this getter

public static string ConnectionStringExcel => @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" +
                                       filename + "; Extended Properties= 'Excel 12.0 Xml;HDR=YES;'";

This will cause the string to be constructed with every call to ConnectionStringExcel

EDIT

If you're using an old version of the .net framework you can use

public static string ConnectionStringExcel 
{
   get 
   { 
      return @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" +
                                       filename + "; Extended Properties= 'Excel 12.0 Xml;HDR=YES;'"; 
   } 
}

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