字符串作为新类的私有字段

/**
* MyClass is an immutable class, since there is no way to change
* its state after construction.
*/

public final class MyClass{

private final String myString;

public MyClass(String myString){
   this.myString = myString;
}

 /**
  * Returns an immutable object. String is immutable.
  *
  */

public String getMyString(){
   return myString;
}

//no need to provide a setter to keep myString as immutable after initial state
}