A Java compiler is a compiler for the programming language Java. The most common form of output from a Java compiler is Java class files containing platform-neutral Java bytecode, but there are also compilers that output optimized native machine code for a particular hardware/operating system combination.

Most Java-to-bytecode compilers, Jikes being a well known exception, do virtually no optimization, leaving this until run time to be done by the JRE.^{[citation needed]}

The Java virtual machine (JVM) loads the class files and either interprets the bytecode or just-in-time compiles it to machine code and then possibly optimizes it using dynamic compilation.

A standard on how to interact with Java compilers programmatically was specified in JSR 199.

import java.util.Scanner;

class secondmax {
     public static void main (String args[]) {
               int n,temp,fmax=0,smax=0;
               Scanner sc=new Scanner(System.in);
               System.out.println("Enter how many numbers will you enter:");
               n=sc.nextInt();
               for(int i=0; i<n; i++) {
                    temp=sc.nextInt();
                    if(i == 0) {
                       fmax=temp;
                    } else if(temp > fmax) {
                       fmax=temp;
                    }
               }
            
            System.out.println("First max: " + fmax);  
            System.out.println("Second max: " + smax);  
     }           
}

import java.util.Scanner;

public class App {

   public static void main(String[] args) {
       Scanner sc = new Scanner(System.in);
       System.out.print("Enter a Number: ");
       int numb = sc.nextInt();
       if(numb > 0)
       {
           System.out.println("Positive");
       }
       else if(numb < 0)
       {
           System.out.println("Negative");
       }
       else
       {
           System.out.println("Zero");
       }
       sc.close();
   }

}

External links

• Sun's OpenJDK javac page
• JSR 199 Java Compiler API Java Specification Request for invoking the Java compiler from a Java program
• Stephan Diehl, "A Formal Introduction to the Compilation of Java", Software - Practice and Experience, Vol. 28(3), pages 297-327, March 1998.