/*
Mach and Speed of Sound Calculator
Interactive Program to solve Standard Atmosphere Equations
for mach and speed of sound
Calorically imperfect gas modeled for hypersonics
A Java Applet
Version 1.2b - 5 Mar 12
Written by
Tom Benson
Chuck Trefny
Charles Lamp
NASA Glenn Research Center
> NOTICE
>This software is in the Public Domain. It may be freely copied and used in
>non-commercial products, assuming proper credit to the author is given. IT
>MAY NOT BE RESOLD. If you want to use the software for commercial
>products, contact the author.
>No copyright is claimed in the United States under Title 17, U. S. Code.
>This software is provided "as is" without any warranty of any kind, either
>express, implied, or statutory, including, but not limited to, any warranty
>that the software will conform to specifications, any implied warranties of
>merchantability, fitness for a particular purpose, and freedom from
>infringement, and any warranty that the documentation will conform to the
>program, or any warranty that the software will be error free.
>In no event shall NASA be liable for any damages, including, but not
>limited to direct, indirect, special or consequential damages, arising out
>of, resulting from, or in any way connected with this software, whether or
>not based on warranty, contract, tort or otherwise, whether or not injury
>was sustained by persons or property or otherwise, and whether or not loss
>was sustained from, or arose out of the results of, or use of, the software
>or services provided hereunder.
New Test :
* move the choice for units
* add compute button
* remove Mars model
* add calorically imperfect gas
correct error at low Mach number
TJB 5 Mar 12
*/
import java.awt.*;
import java.lang.Math ;
public class Mach extends java.applet.Applet {
double gama,alt,temp,press,vel,ttot ;
double rgas, rho0, rho, a0, lrat, mach ;
double Q, TT, T, M, GAM, R, A, V, G ;
int lunits,vparam,tparam,ther,prs, planet ;
int mode ;
In in ;
public void init() {
setLayout(new GridLayout(1,1,0,0)) ;
setDefaults () ;
in = new In(this) ;
add(in) ;
computeMach() ;
}
public Insets insets() {
return new Insets(10,10,10,10) ;
}
public void setDefaults() {
vparam = 0 ;
tparam = 0 ;
lunits = 0;
mode = 0 ;
alt = 0.0 ;
V = vel = 500. ;
T = temp = 518.6 - 3.56 * alt/1000. ;
a0 = Math.sqrt(gama*rgas*temp) ; // feet /sec
A = a0 = a0 * 60.0 / 88. ; // mph
M = mach = vel/a0 ;
TT = ttot = temp * (1.0 + (gama - 1.0) * mach * mach) ;
Q = 5500 ;
R = 53.3 ;
}
public double CAL_SOS (double T, double G, double R, double Q) {
double WOW = 1 + (G - 1) / (1 + (G - 1) * Math.pow((Q / T), 2) *
Math.exp(Q / T) / Math.pow((Math.exp(Q / T) - 1), 2));
return (Math.sqrt(32.174 * T * R * WOW));
}
public double TQTT(double M, double G) {
return Math.pow((1 + (G - 1) / 2 * Math.pow(M, 2)), -1);
}
public double CAL_GAM (double T, double G, double Q) {
return (1 + (G - 1) / (1 + (G - 1) * (Math.pow((Q / T), 2) *
Math.exp(Q / T) / Math.pow((Math.exp(Q / T) - 1), 2))));
}
public double CAL_TT (double T, double M, double G, double Q) {
double TT = T / TQTT(M,G);
double EPS = 0.00001;
double Z = 1;
double Z2 = 0;
double TT2 = 0;
double TT1;
double Z1;
double i = 1;
while (Math.abs(Z) > EPS)
{
Z = Math.pow(M, 2) - 2 * TT / CAL_GAM(T, G, Q) / T *
(G / (G - 1) * (1 - T / TT) + Q / TT *
(1 / (Math.exp(Q / TT) - 1) - 1 / (Math.exp(Q / T) - 1)));
if (i == 1)
{
Z2=Z;
TT2 = TT;
TT = TT2 + 100;
i = 2;
}
else
{
TT1 = TT2;
Z1 = Z2;
TT2 = TT;
Z2 = Z;
TT = TT2 - Z2 * (TT2 - TT1) / (Z2 - Z1);
}
}
if (M <= .1) TT = T / TQTT(M,G);
return TT;
}
double CAL_T (double TT, double M, double G, double Q)
{
double T = TT * TQTT(M,G);
double EPS = 0.00001;
double Z=1;
double Z2 = 0;
double T2 = 0;
double T1;
double Z1;
double i=1;
while (Math.abs(Z) > EPS)
{
Z = Math.pow(M, 2) - 2 * TT / CAL_GAM(T, G, Q) / T *
(G / (G - 1) * (1 - T / TT) + Q / TT *
(1 / (Math.exp(Q / TT) - 1) - 1 / (Math.exp(Q / T) - 1)));
if (i==1)
{
Z2 = Z;
T2 = T;
T = T2 + 100;
i=2;
}
else
{
T1 = T2;
Z1 = Z2;
T2 = T;
Z2 = Z;
T = T2 - Z2 * (T2 - T1) / (Z2 - Z1);
}
}
if (M <= .1) T = TT * TQTT(M,G);
return T;
}
double CAL_TV (double TT, double V, double G, double Q)
{
double T = TT - (G -1.0) * V * V / (2.0 * G * R * 32.2);
double EPS = 0.00001;
double Z=1;
double Z2 = 0;
double T2 = 0;
double T1;
double Z1;
double i=1;
while (Math.abs(Z) > EPS)
{
Z = Math.pow(V, 2) - 2 * R * 32.2 * TT *
(G / (G - 1) * (1 - T / TT) + Q / TT *
(1 / (Math.exp(Q / TT) - 1) - 1 / (Math.exp(Q / T) - 1)));
if (i==1)
{
Z2 = Z;
T2 = T;
T = T2 + 100;
i=2;
}
else
{
T1 = T2;
Z1 = Z2;
T2 = T;
Z2 = Z;
T = T2 - Z2 * (T2 - T1) / (Z2 - Z1);
}
}
if (V <= 100.) T = TT - (G -1.0) * V * V / (2.0 * G * R * 32.2);
return T;
}
public void computeMach() {
// Earth standard day
rgas = 1718. ; /* ft2/sec2 R */
G = gama = 1.4 ;
if (tparam == 0) {
if (alt <= 36152.) { // Troposphere
T = temp = 518.6 - 3.56 * alt/1000. ;
}
if (alt >= 36152. && alt <= 82345.) { // Stratosphere
T = temp = 389.98 ;
}
if (alt >= 82345. && alt <= 155348.) {
T = temp = 389.98 + 1.645 * (alt-82345.)/1000. ;
}
if (alt >= 155348. && alt <= 175346.) {
T = temp = 508.788 ;
}
if (alt >= 175346. && alt <= 262448.) {
T = temp = 508.788 - 2.46888 * (alt-175346.)/1000. ;
}
a0 = Math.sqrt(gama*rgas*temp) ; // feet /sec
a0 = a0 * 60.0 / 88. ; // mph
A = CAL_SOS(T, G, R, Q) ;
A = A * 60.0 / 88. ; // mph
// compute either mach or velocity
if (vparam == 0) {
mach = vel/a0 ;
M = V / A ;
}
if (vparam == 1) {
vel = mach * a0 ;
V = M * A ;
}
ttot = temp * (1.0 + .5 * (gama - 1.0) * mach * mach) ;
TT = CAL_TT(T, M, G, Q) ;
GAM = CAL_GAM(T ,G, Q) ;
}
if (tparam == 1) {
if (vparam == 1) {
temp = ttot / (1.0 + .5 * (gama - 1.0) * mach * mach) ;
a0 = Math.sqrt(gama*rgas*temp) ; // feet /sec
a0 = a0 * 60.0 / 88. ; // mph
vel = mach * a0 ;
T = CAL_T(TT, M, G, Q) ;
A = CAL_SOS(T, G, R, Q) ;
A = A * 60.0 / 88. ; // mph
V = M * A ;
GAM = CAL_GAM(T ,G, Q) ;
}
if (vparam == 0) {
V = vel = vel * 88. / 60. ; // v in ft/sec
temp = ttot - (gama -1.0) * vel * vel / (2.0 * gama * rgas) ;
a0 = Math.sqrt(gama*rgas*temp) ; // feet /sec
mach = vel / a0 ;
a0 = a0 * 60.0 / 88. ; // mph
vel = vel * 60. / 88. ; // v in mph
T = CAL_TV(TT, V, G, Q) ;
A = CAL_SOS(T, G, R, Q) ;
GAM = CAL_GAM(T ,G, Q) ;
M = V / A ;
A = A * 60.0 / 88. ; // mph
V = V * 60. / 88. ; // v in mph
}
}
if (lunits == 0) {
in.dn.o3.setText(String.valueOf(filter0(a0))) ;
in.dn.o4.setText(String.valueOf(filter0(vel))) ;
in.dn.o6.setText(String.valueOf(filter0(temp))) ;
in.dn.o8.setText(String.valueOf(filter0(ttot))) ;
in.dn.o3r.setText(String.valueOf(filter0(A))) ;
in.dn.o4r.setText(String.valueOf(filter0(V))) ;
in.dn.o6r.setText(String.valueOf(filter0(T))) ;
in.dn.o8r.setText(String.valueOf(filter0(TT))) ;
}
if (lunits == 1) {
in.dn.o3.setText(String.valueOf(filter0(a0 * .447))) ;
in.dn.o4.setText(String.valueOf(filter0(vel * .447))) ;
in.dn.o6.setText(String.valueOf(filter0(temp * 5.0 /9.0))) ;
in.dn.o8.setText(String.valueOf(filter0(ttot * 5.0 /9.0))) ;
in.dn.o3r.setText(String.valueOf(filter0(A * .447))) ;
in.dn.o4r.setText(String.valueOf(filter0(V * .447))) ;
in.dn.o6r.setText(String.valueOf(filter0(T * 5.0 /9.0))) ;
in.dn.o8r.setText(String.valueOf(filter0(TT * 5.0 /9.0))) ;
}
in.dn.o5.setText(String.valueOf(filter3(mach))) ;
in.dn.o7.setText(String.valueOf(filter3(gama))) ;
in.dn.o5r.setText(String.valueOf(filter3(M))) ;
in.dn.o7r.setText(String.valueOf(filter3(GAM))) ;
if (mode == 0) loadInpt() ;
}
public void loadInpt() {
if (lunits == 0) {
if (vparam == 0) {
in.up.o2.setText(String.valueOf(filter0(vel))) ;
}
if (vparam == 1) {
in.up.o2.setText(String.valueOf(filter3(mach))) ;
}
if (tparam == 0) {
in.up.o1.setText(String.valueOf(filter0(alt))) ;
}
if (tparam == 1) {
in.up.o1.setText(String.valueOf(filter0(ttot))) ;
}
}
if (lunits == 1) {
if (vparam == 0) {
in.up.o2.setText(String.valueOf(filter0(vel*.447))) ;
}
if (vparam == 1) {
in.up.o2.setText(String.valueOf(filter3(mach))) ;
}
if (tparam == 0) {
in.up.o1.setText(String.valueOf(filter0(alt*.3048))) ;
}
if (tparam == 1) {
in.up.o1.setText(String.valueOf(filter0(ttot*5.0/9.0))) ;
}
}
}
public int filter0(double inumbr) {
// integer output
float number ;
int intermed ;
intermed = (int) (inumbr) ;
number = (float) (intermed);
return intermed ;
}
public float filter3(double inumbr) {
// output only to .001
float number ;
int intermed ;
intermed = (int) (inumbr * 1000.) ;
number = (float) (intermed / 1000. );
return number ;
}
public float filter5(double inumbr) {
// output only to .00001
float number ;
int intermed ;
intermed = (int) (inumbr * 100000.) ;
number = (float) (intermed / 100000. );
return number ;
}
class In extends Panel {
Mach outerparent ;
Titl titl ;
Up up ;
Dn dn ;
In (Mach target) {
outerparent = target ;
setLayout(new GridLayout(3,1,5,5)) ;
titl = new Titl(outerparent) ;
up = new Up(outerparent) ;
dn = new Dn(outerparent) ;
add(titl) ;
add(up) ;
add(dn) ;
}
public Insets insets() {
return new Insets(5,5,0,0) ;
}
class Titl extends Panel {
Label la ;
In2 in2;
Titl (Mach target) {
outerparent = target ;
setLayout(new GridLayout(2,1,0,0)) ;
la = new Label("Mach and Speed of Sound Calculator", Label.CENTER) ;
la.setForeground(Color.red) ;
in2 = new In2(outerparent) ;
add(la) ;
add(in2) ;
}
class In2 extends Panel {
Label lc,lb ;
Choice plntch,untch ;
In2 (Mach target) {
outerparent = target ;
setLayout(new GridLayout(2,4,0,0)) ;
lb = new Label("Units:", Label.RIGHT) ;
lb.setForeground(Color.red) ;
untch = new Choice() ;
untch.addItem("Imperial") ;
untch.addItem("Metric");
untch.setBackground(Color.white) ;
untch.setForeground(Color.red) ;
untch.select(0) ;
add(new Label(" ", Label.RIGHT)) ;
add(lb) ;
add(untch) ;
add(new Label(" ", Label.RIGHT)) ;
add(new Label(" ", Label.RIGHT)) ;
add(new Label(" ", Label.RIGHT)) ;
add(new Label(" ", Label.RIGHT)) ;
add(new Label(" ", Label.RIGHT)) ;
}
public boolean handleEvent(Event evt) {
if(evt.id == Event.ACTION_EVENT) {
lunits = untch.getSelectedIndex() ;
if (lunits == 0) { // English units labels
dn.l4.setText("Object Speed - mph") ;
dn.l3.setText("Speed of Sound - mph") ;
dn.l6.setText("Static Temperature - R") ;
dn.l8.setText("Total Temperature - R") ;
if (vparam == 0) {
up.l2u.setText("mph") ;
}
if (vparam == 1) {
up.l2u.setText(" ") ;
}
if (tparam == 0) {
up.l1u.setText("feet") ;
}
if (tparam == 1) {
up.l1u.setText("R") ;
}
}
if (lunits == 1) { // Metric units labels
dn.l4.setText("Object Speed - m/sec") ;
dn.l3.setText("Speed of Sound - m/sec") ;
dn.l6.setText("Static Temperature - K") ;
dn.l8.setText("Total Temperature - K") ;
if (vparam == 0) {
up.l2u.setText("m/sec") ;
}
if (vparam == 1) {
up.l2u.setText(" ") ;
}
if (tparam == 0) {
up.l1u.setText("meters") ;
}
if (tparam == 1) {
up.l1u.setText("K") ;
}
}
mode = 0 ;
computeMach() ;
return true ;
}
else return false ;
}
}
}
class Up extends Panel {
TextField o1,o2 ;
Label l1,l1u,l2u, la ;
Button bt1;
Choice vch,tch ;
Up (Mach target) {
outerparent = target ;
setLayout(new GridLayout(4,4,5,5)) ;
la = new Label("Input", Label.LEFT) ;
la.setForeground(Color.red) ;
l1u = new Label(" feet ", Label.CENTER) ;
o1 = new TextField() ;
o1.setBackground(Color.white) ;
o1.setForeground(Color.black) ;
l2u = new Label("mph", Label.CENTER) ;
o2 = new TextField() ;
o2.setBackground(Color.white) ;
o2.setForeground(Color.black) ;
vch = new Choice() ;
vch.addItem("Object Speed") ;
vch.addItem("Mach");
vch.select(0) ;
tch = new Choice() ;
tch.addItem("Altitude") ;
tch.addItem("Total Temperature");
tch.select(0) ;
bt1 = new Button("COMPUTE") ;
bt1.setBackground(Color.red) ;
bt1.setForeground(Color.white) ;
add(la) ;
add(new Label(" ", Label.RIGHT)) ;
add(new Label(" ", Label.RIGHT)) ;
add(new Label(" ", Label.RIGHT)) ;
add(new Label(" ", Label.RIGHT)) ;
add(vch) ;
add(o2) ;
add(l2u) ;
add(new Label(" ", Label.RIGHT)) ;
add(tch) ;
add(o1) ;
add(l1u) ;
add(new Label(" ", Label.RIGHT)) ;
add(new Label("Press -> ", Label.RIGHT)) ;
add(bt1) ;
add(new Label(" ", Label.RIGHT)) ;
}
public Insets insets() {
return new Insets(5,5,5,5) ;
}
public boolean action(Event evt, Object arg) {
if(evt.target instanceof Choice) {
this.handleProb(arg) ;
return true ;
}
if(evt.target instanceof Button) {
this.handleBut(evt) ;
return true ;
}
else return false ;
}
public void handleProb(Object obj) {
vparam = vch.getSelectedIndex() ;
tparam = tch.getSelectedIndex() ;
if (lunits == 0) { // English units labels
if (vparam == 0) {
l2u.setText("mph") ;
}
if (vparam == 1) {
l2u.setText(" ") ;
}
if (tparam == 0) {
l1u.setText("feet") ;
}
if (tparam == 1) {
l1u.setText("R") ;
}
}
if (lunits == 1) { // Metric units labels
if (vparam == 0) {
l2u.setText("m/sec") ;
}
if (vparam == 1) {
l2u.setText(" ") ;
}
if (tparam == 0) {
l1u.setText("meters") ;
}
if (tparam == 1) {
l1u.setText("K") ;
}
}
mode = 0 ;
computeMach() ;
}
public void handleBut(Event evt) {
Double V1,V2 ;
double v1,v2 ;
V1 = Double.valueOf(o1.getText()) ;
v1 = V1.doubleValue() ;
V2 = Double.valueOf(o2.getText()) ;
v2 = V2.doubleValue() ;
if (lunits == 0) {
if (vparam == 0) {
if (v2 < 0.0) {
v2 = 0.0 ;
o2.setText(String.valueOf(filter0(v2))) ;
}
if (v2 >17600.0) {
v2 = 17600.0 ;
o2.setText(String.valueOf(filter0(v2))) ;
}
V = vel = v2 ;
}
if (vparam == 1) {
if (v2 < 0.0) {
v2 = 0.0 ;
o2.setText(String.valueOf(filter0(v2))) ;
}
if (v2 >25.0) {
v2 = 25.0 ;
o2.setText(String.valueOf(filter0(v2))) ;
}
M = mach = v2 ;
}
if (tparam == 0) {
if (v1 < 0.0) {
v1 = 0.0 ;
o1.setText(String.valueOf(filter0(v1))) ;
}
if (v1 >250000.0) {
v1 = 250000.0 ;
o1.setText(String.valueOf(filter0(v1))) ;
}
alt = v1 ;
}
if (tparam == 1) {
if (v1 < 500.0) {
v1 = 500.0 ;
o1.setText(String.valueOf(filter0(v1))) ;
}
if (v1 >5000.0) {
v1 = 5000.0 ;
o1.setText(String.valueOf(filter0(v1))) ;
}
TT = ttot = v1 ;
}
}
if (lunits == 1) {
if (vparam == 0) {
if (v2 < 0.0) {
v2 = 0.0 ;
o2.setText(String.valueOf(filter0(v2))) ;
}
if (v2 >7867.0) {
v2 = 7867.0 ;
o2.setText(String.valueOf(filter0(v2))) ;
}
V = vel = v2 / .447 ;
}
if (vparam == 1) {
if (v2 < 0.0) {
v2 = 0.0 ;
o2.setText(String.valueOf(filter0(v2))) ;
}
if (v2 >25.0) {
v2 = 25.0 ;
o2.setText(String.valueOf(filter0(v2))) ;
}
M = mach = v2 ;
}
if (tparam == 0) {
if (v1 < 0.0) {
v1 = 0.0 ;
o1.setText(String.valueOf(filter0(v1))) ;
}
if (v1 >76200.0) {
v1 = 76200.0 ;
o1.setText(String.valueOf(filter0(v1))) ;
}
alt = v1 / .3048 ;
}
if (tparam == 1) {
if (v1 < 277.7) {
v1 = 277.7 ;
o1.setText(String.valueOf(filter0(v1))) ;
}
if (v1 >2777.7) {
v1 = 2777.7 ;
o1.setText(String.valueOf(filter0(v1))) ;
}
TT = ttot = v1 * 9.0 / 5.0 ;
}
}
mode = 1;
computeMach() ;
}
}
class Dn extends Panel {
Mach outerparent ;
TextField o3,o4,o5,o6,o7,o8 ;
TextField o3r,o4r,o5r,o6r,o7r,o8r ;
Label l3,l4,l5,l6,l7,l8 ;
Label lb,lc,ld ;
Dn (Mach target) {
outerparent = target ;
setLayout(new GridLayout(7,4,0,0)) ;
lb = new Label("Output", Label.LEFT) ;
lb.setForeground(Color.blue) ;
lc = new Label("Perfect", Label.CENTER) ;
lc.setForeground(Color.blue) ;
ld = new Label("Calorically Imperfect", Label.CENTER) ;
ld.setForeground(Color.blue) ;
l3 = new Label("Speed of Sound - mph", Label.CENTER) ;
o3 = new TextField() ;
o3.setBackground(Color.black) ;
o3.setForeground(Color.yellow) ;
o3r = new TextField() ;
o3r.setBackground(Color.black) ;
o3r.setForeground(Color.cyan) ;
l4 = new Label("Object Speed - mph", Label.CENTER) ;
o4 = new TextField() ;
o4.setBackground(Color.black) ;
o4.setForeground(Color.yellow) ;
o4r = new TextField() ;
o4r.setBackground(Color.black) ;
o4r.setForeground(Color.cyan) ;
l5 = new Label("Mach", Label.CENTER) ;
o5 = new TextField() ;
o5.setBackground(Color.black) ;
o5.setForeground(Color.yellow) ;
o5r = new TextField() ;
o5r.setBackground(Color.black) ;
o5r.setForeground(Color.cyan) ;
l6 = new Label("Static Temperature - R", Label.CENTER) ;
o6 = new TextField() ;
o6.setBackground(Color.black) ;
o6.setForeground(Color.yellow) ;
o6r = new TextField() ;
o6r.setBackground(Color.black) ;
o6r.setForeground(Color.cyan) ;
l7 = new Label("Gamma", Label.CENTER) ;
o7 = new TextField() ;
o7.setBackground(Color.black) ;
o7.setForeground(Color.yellow) ;
o7r = new TextField() ;
o7r.setBackground(Color.black) ;
o7r.setForeground(Color.cyan) ;
l8 = new Label("Total Temperature - R", Label.CENTER) ;
o8 = new TextField() ;
o8.setBackground(Color.black) ;
o8.setForeground(Color.yellow) ;
o8r = new TextField() ;
o8r.setBackground(Color.black) ;
o8r.setForeground(Color.cyan) ;
add(lb) ;
add(new Label(" ", Label.RIGHT)) ;
add(lc) ;
add(ld) ;
add(new Label(" ", Label.RIGHT)) ;
add(l4) ;
add(o4) ;
add(o4r) ;
add(new Label(" ", Label.RIGHT)) ;
add(l3) ;
add(o3) ;
add(o3r) ;
add(new Label(" ", Label.RIGHT)) ;
add(l5) ;
add(o5) ;
add(o5r) ;
add(new Label(" ", Label.RIGHT)) ;
add(l6) ;
add(o6) ;
add(o6r) ;
add(new Label(" ", Label.RIGHT)) ;
add(l8) ;
add(o8) ;
add(o8r) ;
add(new Label(" ", Label.RIGHT)) ;
add(l7) ;
add(o7) ;
add(o7r) ;
}
}
}
}
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}
}
OneCompiler supports Gradle for dependency management. Users can add dependencies in the build.gradle file and use them in their programs. When you add the dependencies for the first time, the first run might be a little slow as we download the dependencies, but the subsequent runs will be faster. Following sample Gradle configuration shows how to add dependencies
apply plugin:'application'
mainClassName = 'HelloWorld'
run { standardInput = System.in }
sourceSets { main { java { srcDir './' } } }
repositories {
jcenter()
}
dependencies {
// add dependencies here as below
implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.9'
}
Java is a very popular general-purpose programming language, it is class-based and object-oriented. Java was developed by James Gosling at Sun Microsystems ( later acquired by Oracle) the initial release of Java was in 1995. Java 17 is the latest long-term supported version (LTS). As of today, Java is the world's number one server programming language with a 12 million developer community, 5 million students studying worldwide and it's #1 choice for the cloud development.
short x = 999; // -32768 to 32767
int x = 99999; // -2147483648 to 2147483647
long x = 99999999999L; // -9223372036854775808 to 9223372036854775807
float x = 1.2;
double x = 99.99d;
byte x = 99; // -128 to 127
char x = 'A';
boolean x = true;
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
// code
} else {
// code
}
Example:
int i = 10;
if(i % 2 == 0) {
System.out.println("i is even number");
} else {
System.out.println("i is odd number");
}
Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.
switch(<conditional-expression>) {
case value1:
// code
break; // optional
case value2:
// code
break; // optional
...
default:
//code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition. Usually for loop is preferred when number of iterations is known in advance.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while(<condition>){
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (<condition>);
Class is the blueprint of an object, which is also referred as user-defined data type with variables and functions. Object is a basic unit in OOP, and is an instance of the class.
class keyword is required to create a class.
class Mobile {
public: // access specifier which specifies that accessibility of class members
string name; // string variable (attribute)
int price; // int variable (attribute)
};
Mobile m1 = new Mobile();
public class Greeting {
static void hello() {
System.out.println("Hello.. Happy learning!");
}
public static void main(String[] args) {
hello();
}
}
Collection is a group of objects which can be represented as a single unit. Collections are introduced to bring a unified common interface to all the objects.
Collection Framework was introduced since JDK 1.2 which is used to represent and manage Collections and it contains:
This framework also defines map interfaces and several classes in addition to Collections.
| Collection | Description |
|---|---|
| Set | Set is a collection of elements which can not contain duplicate values. Set is implemented in HashSets, LinkedHashSets, TreeSet etc |
| List | List is a ordered collection of elements which can have duplicates. Lists are classified into ArrayList, LinkedList, Vectors |
| Queue | FIFO approach, while instantiating Queue interface you can either choose LinkedList or PriorityQueue. |
| Deque | Deque(Double Ended Queue) is used to add or remove elements from both the ends of the Queue(both head and tail) |
| Map | Map contains key-values pairs which don't have any duplicates. Map is implemented in HashMap, TreeMap etc. |