Chapter 5: Preparing Java Programs

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Chapter 5

Preparing Java Programs

Chapter 5 Program development 2

Program development

EDIT

Understanding the problem

Writing an algorithm

Converting to code

COMPILE

RUN

errors

Result

Verifying the algorithm

Chapter 5 Program development 3

Program development

EDIT

COMPILE

RUN

errors

Result

Source code

pico prog.java

javac prog.java

java prog

Chapter 5 High-level languages 4

High-level languages

Machine language: computer’s native language.

Add two numbers: 00100111 1010 0101Assembly language: uses mnemonics.

Add two numbers: ADD R1 R2

An assembly code needs to be translated to machine code.

Chapter 5 High-level languages 5

High-level languages

High-level programming languages: bridging the gap between machine language and natural languages.

Examples: COBOL, Fortran, Algol, C

Add two numbers (in C): Z = A + B;Compilation: translation to machine code.

Chapter 5 A Java program 6

A Java programA sample Java program// A Java program to read a number and compute and display its square.

import java.io.*;

class square {

public static void main(String arg[]) throws IOException {

int n;

BufferedReader stdin = new BufferedReader

(new InputStreamReader (System.in));

System.out.print ("Enter the number to be square: ");

n = Integer.parseInt (stdin.readLine());

System.out.println ("The square of " + n + " is " + n*n);

}

}

Chapter 5 Compilation in Java 7

Compilation in Java

Use the javac command to compile:javac prog.java

Produces the object file with extension .class (eg: prog.class)

To run object file, use the java command:java prog

Chapter 5 Errors 8

Errors

Compilation errors: occur during compilation. Reason: syntax errors.

Easy to rectify.

Run-time errors: occur during execution. Reasons: logic errors, data errors, computation

errors. Harder to rectify.

Chapter 5 Homework 9

Homework