How to convert a char to a String?

Question

I have a char and I need a String. How do I convert from one to the other?

Answer 1

You can use Character.toString(char). Note that this method simply returns a call to String.valueOf(char), which also works.

As others have noted, string concatenation works as a shortcut as well:

String s = "" + 's'; 

But this compiles down to:

String s = new StringBuilder().append("").append('s').toString(); 

which is less efficient because the StringBuilder is backed by a char[] (over-allocated by StringBuilder() to 16), only for that array to be defensively copied by the resulting String.

String.valueOf(char) "gets in the back door" by wrapping the char in a single-element array and passing it to the package private constructor String(char[], boolean), which avoids the array copy.

Answer 2

I've got of the following five six methods to do it.

// Method #1 String stringValueOf = String.valueOf('c'); // most efficient  // Method #2 String stringValueOfCharArray = String.valueOf(new char[]{x});  // Method #3 String characterToString = Character.toString('c');  // Method #4 String characterObjectToString = new Character('c').toString();  // Method #5 // Although this approach seems very simple,  // this is less efficient because the concatenation // expands to a StringBuilder. String concatBlankString = 'c' + "";  // Method #6 String fromCharArray = new String(new char[]{x}); 

Note: Character.toString(char) returns String.valueOf(char). So effectively both are same.

String.valueOf(char[] value) invokes new String(char[] value), which in turn sets the value char array.

public String(char value[]) {     this.value = Arrays.copyOf(value, value.length); } 

On the other hand String.valueOf(char value) invokes the following package private constructor.

String(char[] value, boolean share) {     // assert share : "unshared not supported";     this.value = value; } 

Source code from String.java in Java 8 source code

Hence String.valueOf(char) seems to be most efficient method, in terms of both memory and speed, for converting char to String.

Sources:

1. How to convert primitive char to String in Java
2. How to convert Char to String in Java with Example