Createing string objects

Question

String s= new String("abc");
String s1="abc";Is there any performence issue between these two?
I think both will take same time to create objects.

Answer 1

Yes, there is a performance implication.
When using the first line String s = new String("abc"); you are actually creating two objects. As a general rule, you should never use a String class constructor when initializing to a literal value. Even doing String s = new String("abc" + someVariable) is creating one more object than needed. "abc" is the firs object, the result of "abc" + someVariable is the second object, and the String created by the constructor is the third.
It should be noted most recent JVMs use some level of caching of String Literal value objects (I believe this goes as far back as JDK 1.3), such that "abc" is only be created once by the JVM (though I'm not sure if it will cache all literal String objects or use some type of LRU algorthm to discard some of them). Regardless, there is some level of efficiency you get from the JVM doing this. Thus if a method containing String s = "abc" is called repeatedly, a reference to the same String object should be used everytime; there will be no further creations of the object as long as the JVM keeps it in cache.
Using String s= new String("abc") will leverage the cached literal reference to "abc", but also creates a new instance of String to refer to the literal everytime your method is called. This is much less efficient.
Run the following code (I did it using JDK 6):
package org.einsteinium.samples;
public class StringTest {
     public static void main(String[] args) {
          String s1 = "abc";
          String s2 = "abc";
          boolean equalMethodTest = s1.equals(s2);
          System.out.println("Are the objects the same using the equals method? " + equalMethodTest);
          boolean equalOperatorTest = (s1 == s2);
          System.out.println("Are the objects the same using the equal operator? " + equalOperatorTest);
}It will print:
Are the objects the same using the equals method? true
Are the objects the same using the equal operator? trueNow if you re-write it to:
package org.einsteinium.samples;
public class StringTest {
     public static void main(String[] args) {
          String s1 = new String("abc");
          String s2 = "abc";
          boolean equalMethodTest = s1.equals(s2);
          System.out.println("Are the objects the same using the equals method? " + equalMethodTest);
          boolean equalOperatorTest = (s1 == s2);
          System.out.println("Are the objects the same using the equal operator? " + equalOperatorTest);
}it will print:
Are the objects the same using the equals method? true
Are the objects the same using the equal operator? falseI hope this helps some.