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Stream is an iterator that allows you to refer to the storage elements of a collection one by one and process them in a lambda expression, which has been added since Java 8. It acts similar to an Iterator, but the difference is that the code can be made more concise by providing the element handling code in a lambda expression, and that parallelism is easy because it uses an internal iterator. I..

var : 1. can be declared with any datatype for a local variable public class VarKeyword { public static void main(String[] args) { // local variale var a = 10; // local variale var b = 1.2; // Java can infer what type is declared System.out.println(String.format("result:\n%d", a)); System.out.println(b); } }2. can not be used in an instance and global variable 3. cannot be used in a Generic type..

Factor String StringBuilder StringBuffer Storage Area String Pool Heap Area Heap Area Mutability Immutable Mutable Mutable Performance slow Fast middle Java Version 1.0 1.5 1.2

Java Development Kit(JDK) Java Runtime Environment(JRE) Java Virtual Machine(JVM) JRE + Development tools JVM + Libraries to execute the application Runtime environment to execute Java byte code JRE, JavaDoc, compiler, debuggers, and so on. software package(Java class libraries, JVM, and so on.) Specification, Implement, and Runtime Instance.