String str = new String("SOME")
always create a new object on the heap
String str="SOME"
uses the String pool
Try this small example:
String s1 = new String("hello");
String s2 = "hello";
String s3 = "hello";
System.err.println(s1 == s2);
System.err.println(s2 == s3);
To avoid creating unnecesary objects on the heap use the second form.