iT-15-[Javaå匷ð¥]
Javaã£ãŠã楜ããã
埩ç¿ð¥
ã»é å
é åã¯ãâãnew
ããŒã¿å[] é
ååã= new ããŒã¿å[èŠçŽ æ°]
int[] score = new int[3];
score[0] = 80;
// scoreã®ïŒçªç®ã«ã80ã代å
¥ããŠãã ããããæ·»åã¯ã0ããã¹ã¿ãŒãããããšã«æ³šæ
é åã®åæå
ããŒã¿å[] é
ååã= { å€1, å€2, ã»ã»ã»ã»}
é
å.length ã§ãé
åã®èŠçŽ æ°ãGet
class Array {
public static void main(String args[]) {
int[] score = new int[3]
score[0] = 80;
score[1] = 100;
score[2] = 70;
String[] name = {"é«æš", "西山", "å°æ¢
"};
System.out.println(name[0] + "ãã:" + score[0] + "ç¹");
System.out.println(name[1] + "ãã:" + score[1] + "ç¹");
System.out.println(name[2] + "ãã:" + score[2] + "ç¹");
System.out.println("åéšè
æ°:" + score.length + "人ã§ãã");
// score.lengthãããããšã§ããã®èŠçŽ ã®æ°ïŒèŠçŽ æ°ïŒãå©çšããããšãã§ããïŒïŒãããã
}
}
å€æ¬¡å é å
class MultiArray{
public static void main(String[] args){
int[][] allScore = new int[2][3];
allScore[0][0] = 80;
allScore[0][1] = 100;
allScore[0][2] = 75;
allScore[1][0] = 85;
allScore[1][1] = 95;
allScore[1][2] = 80;
// å€æ¬¡å
é
åã®åæå
// int[][] allScore = { {10, 20, 30}, {40, 50, 60} };
System.out.println(allScore[0][0] + "ç¹");
System.out.println(allScore[0][1] + "ç¹");
System.out.println(allScore[0][2] + "ç¹");
System.out.println(allScore[1][0] + "ç¹");
System.out.println(allScore[1][1] + "ç¹");
System.out.println(allScore[1][2] + "ç¹");
System.out.println("allScore.lengthïŒ" + allScore.length);
System.out.println("allScore[0].lengthïŒ" + allScore[0].length);
}
}
ã»æŒç®å
ç®è¡æŒç®å
//å²ãç®
7 / 2 â 3
//ããŸãã®æ°
7 % 2 â 1
ä»£å ¥ãè€åä»£å ¥æŒç®å
//a = a + bãšåãã
a += bã
//aã«bãå ããŠãaã«å床代å
¥ããã
ã€ã³ã¯ãªã¡ã³ãããã¯ãªã¡ã³ãæŒç®å
//a = a + 1;ãšåãã
a ++;
a --;
äŸ
class Operator {
public static void main(String[] args){
//ã³ãã³ãã©ã€ã³ããå
¥åããæåååããint aãšããŠå®£èšãã
int a = Integer.parseInt(args[0]);
int b = Integer.parseInt(args[1]);
System.out.println("a =" + a + "b =" + b );
System.out.println("a + b =" + (a + b));
System.out.println("a - b =" + (a - b));
System.out.println("a / b =" + (a / b));
System.out.println("a % b =" + (a % b));
System.out.println("a >= 0 :" + (a >= 0);
System.out.println("(a >= 0) && (b >= 0):" + ((a >= 0)&&(b >= 0));
}
}
é¢ä¿æŒç®å
trueãfalse
è«çæŒç®å
ïŒa >= 0ïŒ&& ïŒb >= 0ïŒ
â&&ã¯ããã€ããè¡šãã
â||ã¯ããããã¯ããè¡šãã
Integer.parseInt()
//æåååãintåã«å€æ
int a = Integer.parseInt(args[0]);
//ã³ãã³ãã©ã€ã³ã§å
¥åããæ°ããäžã®args[0]ã«ä»£å
¥ããããšã«ãªãã
ã»åºæ¬ããŒã¿ã®åå€æ
è¡šçŸã®å¹
ãåºãé ãçãïŒèªåã§ïŒ
double, float, long, int, short, byte
intãâ â«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïž
double â â«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïžâ«ïž
d = i;
//OK
倧ããç®±ãå°ããªç®±ã«ããããå
¥ããïŒä»£å
¥ããïŒããã«ã¯ã
ãã£ã¹ããšãããã®ãå¿
èŠã ãããããããæã«ãªã£ãããããæžãã
i = (int)d;
//OK
ãã£ã¹ãã¯ã()å
ã«ã
å€æåŸã®ããŒã¿åã®ååãå
¥ããå¿
èŠãããã
class FukuKau {
public static void main(String[] args){
int uniform = 1980;
double percent = 0.08;
System.out.println("æã®å€æ®µãïŒç" + uniform + "åã§ãã");
System.out.println("æ¶è²»çšã0.08ïŒ
ãªã®ã§ãåèšéé¡ã¯ã" + (uniform * percent) + "åã§ãã");
}
}
âããã ãšã1980åã®ããã·ã£ããããããå®ããªã£ãŠããŸããªw w
âã€ãŸããïŒåã«ã0.08åãå ç®ããåŠçãæžããªãã£ãã
åŸã«åèã«ããã³ãŒã
class FukuKau {
public static void main(String[] args){
int price = Integer.parseInt(args[0]);
double rate = 0.08;
int amount;
amount = (int)(price * (1 + rate))
System.out.println("çšèŸŒéé¡ã¯ã" + amount + "åã§ãã");
}
}
ãªãã»ã©ïŒïŒ
以äžã¯ãèªåãªãã®è§£èª¬ã§ãã
class FukuKau {
public static void main(String[] args){
//æã®ãã ããå
¥åããããããargs[0]ãåŒæ°ãšãªãpriceã«ä»£å
¥ããŠãããã
int price = Integer.parseInt(args[0]);
ãããããããã
ãããããããã//ïŒ.ïŒïŒã¯ãæµ®åå°æ°ç¹æ°ãšããŠdoubleã§å®£èšãããå€ã代å
¥ããŠããã
double rate = 0.08;
ãããããããã//amountãšããæŽæ°åã宣èšããŠããã
int amount;
ãããããããã/*amountã«ãçšèŸŒéé¡ã®åŒã代å
¥ããããã®ãšããdoubleåã64bit,intåã32bitãªã®ã§ãå°ããª
ããããããããããããç®±ã«ã倧ããªç®±ãããããå
¥ããããšã«ãªãããã®ããããŠãïŒãã£ã¹ãã䜿ãå¿
èŠãããã
ãããããããããããããã£ãŠãïŒintïŒã§å€æåŸã®ããŒã¿åãå
¥ãamountã«ä»£å
¥ããŠããããã*/
ãããããããããããã
amount = (int)(price * (1 + rate))
System.out.println("çšèŸŒéé¡ã¯ã" + amount + "åã§ãã");
}
}
ã»æ§é åããã°ã©ãã³ã°
以äžãçµã¿åãããŠããã°ã©ã ãããããšãæèããŠæžããšãããã°ã©ã ããããããããªãã
â é 次é²è¡
â|åŠç|â|åŠç|â|åŠç|â|åŠç|â|åŠç|â|åŠç|â|åŠç|â|åŠç|â|åŠç|âã»ã»
â¡åå²
â|æ¡ä»¶|âtrueâ|åŠç|â
ããâ â
ãã |â falseâ|åŠç|â |
â¢ç¹°ãè¿ã
â|æ¡ä»¶|â|åŠç|â|æŽæ°ïŒ|â|æ¡ä»¶|â|åŠç|â|æŽæ°ïŒ|â
Ifæ
if (æ¡ä»¶åŒ) {
åŠçïŒ
} else {
ããåŠçïŒ
ãããã}
ã»ã©ã¡ããã®åŠçããå®è¡ãããªãã
ã»else以éã¯ãçç¥ã§ããã
ã»åŠçã1ã€ã®ãšãã¯ã{}ã¯æžããªããŠè¯ãã
ããã·ã£ãã3000å以äžãããšããã£ã¹ã«ãŠã³ããããããã°ã©ã ãäœæããŠã¿ãã
èªåã®ã³ãŒã
class FukuKau2{
public static void main(String[] args){
int price = Integer.parseInt(args[0]);
double rate = 0.08;
int discount, amount;
ããããããããamount = (int)(price * (1 + rate));
if(price >= 3000){
discount = 300;
System.out.println("å²åŒãããã®ã§ãéé¡ã¯"ã+ (amount - discount) + "å");
} else {
System.out.println("å²åŒã¯ãªãã®ã§ã" + amount + "å");
}
}
}
if(price >= 3000){
discount = 300;
} else {
discount = 0;
}
å匷ð¥ð¥
ã»else ifæ
if(price >= 3000){
discount = 300;
} else {
discount = 0;
}
ã®æ¡åŒµïŒïŒããã«æ¡ä»¶åŒãå ¥ããå Žåã¯ãã¡ãã
if(æ¡ä»¶åŒ1){
åŠçïŒ;
} else if (æ¡ä»¶åŒ2)
åŠçïŒ;
} else {
åŠç3;
}
ã»swichæ
swich(åŒ){
case1:
åŠç1
break1;
case2:
åŠç2
break2;
case3:
åŠç3
break3;
}
ã»åŒã«å
¥ãã®ã¯ãbyte, short, int, charåã§ããã
ã»åŒã®å€ã«ãã£ãŠãåŠçã®éå§äœçœ®ã決ãŸãïŒïŒ
ã»breakã¯äœããšãããšããã{ã}ãæããŸãïŒãšããæå³ã
ã»whileæ
while(æ¡ä»¶åŒ){
åŠç
case1:
åŠç1
break1;
case2:
åŠç2
break2;
case3:
åŠç3
break3;
}
åé¡ð¥ð¥ð¥
ã»ïŒå
é¢ç©ãšé«ãã»å¹ ã»é¢ç©ã®è¡šç€ºãããªããã
class Triangle{
public static void main(String[] args){
int height = Integer.parseInt(args[0]);
int width = Integer.parseInt(args[1]);
int area;
//é¢ç©ã®èšç®
//é«ãã»å¹
ã»é¢ç©ã®è¡šç€º
}
}
ãããŠãèãããã
ãŸããInteger.parseInt()ã䜿ãããŠãããããå
¥åããæ°ããã®ãŸãŸé¢ç©ãæ±ããããããã«ãªã£ãŠããã¯ãã ã
ã ãããé«ãâïžå¹
(暪)ããé¢ç©ã®èšç®ã«ãªãã®ã§ã»ã»ã»
ãšãããããé¢ç©ãareaã§intåïŒæŽæ°åïŒã§å®£èšãããŠãããããããã䜿ãã®ã ãªã
ããïŒå€åããã ã
以äžãèªåãªãã«èããã³ãŒã
class Triangle{
public static void main(String[] args){
int height = Integer.parseInt(args[0]);
int width = Integer.parseInt(args[1]);
int area;
//é¢ç©ã®èšç®
ããããããããarea = ((height * width) / 2);
//é«ãã»å¹
ã»é¢ç©ã®è¡šç€º
System.out.println("é«ãïŒ"ã+ãheightã+ã",å¹
ïŒ"ã+ãwidthã+ã",é¢ç©ïŒ"ã+ãarea);
}
}
ããã§ã©ãã§ãããïŒ
åçã³ãŒã
class Triangle{
public static void main(String[] args){
int height = Integer.parseInt(args[0]);
int width = Integer.parseInt(args[1]);
int area;
//é¢ç©ã®èšç®
area = height * width / 2;
//é«ãã»å¹
ã»é¢ç©ã®è¡šç€º
System.out.println("é«ãïŒ" + height);
System.out.println("å¹
ãïŒ" + width);
System.out.println("é¢ç©ïŒ" + area);
}
}
æŠããã£ãŠãããã®ã®ã
//é¢ç©ã®èšç®
area = height * width / 2;
ããã§ããã®ãã
ïŒïŒãå¿
èŠãªã®ã§ã¯ãªãããšæã£ããã確ãã«ã©ã®é çªã«ãããŠèšç®ããŠãã§ããããOKã ãªã
ã»ïŒå
é¢ç©ãå°æ°ç¹ç¬¬ïŒäœãŸã§è¡šç€ºããããã«ããŠãã ããã
ä»ã®ãŸãŸã ãšãã³ã³ãã€ã«ãšã©ãŒã¯åºãªããã®ã®ã
äŸãã°ååŸrïŒãïŒïŒãšããŠå
¥åãããšã
é¢ç©ã314.1592ãŸã§è¡šç€ºãããããšã«ãªããããã
ã§ã¯ããããå°æ°ç¹ç¬¬ïŒäœãŸã§è¡šç€ºãããšããããšã¯ã
ã³ã³ãã€ã«ããã é¢ç©ã314.15ãŸã§ã«ãªããšããããšã ã
class Sample003{
public static void main(String[] args){
int radius = 15;
double pi = 3.141592;
double area;
double minus;
area = radius * radius * pi;
//å°æ°ç¹ç¬¬ïŒäœä»¥éãåãæšãŠ
System.out.println("ååŸïŒ" + radius);
System.out.println("é¢ç©ïŒ" + area);
}
}
èããŸããããé æ«ããŸããã
//å°æ°ç¹ç¬¬ïŒäœä»¥éãåãæšãŠ
ããããããããminus = area % 0.1;
area = area - minus;
ããèããŸããããããŸããããã
å°æ°ç¹ç¬¬äºä»¥äžããå
ã®èšç®åŒããåŒããããã¿ããª0ã«ãªããšæã£ããã§ããã§ããçµå±0ãåºåãããã®ã§ãåãæšãŠã»ã»ã»ãïŒïŒãšãªã£ãŠããŸãã
åèã³ãŒã
class Circle{
public static void main(String[] args){
int radius = Integer.parseInt(args[0]);
double pi = 3.141592;
double area;
area = radius * radius * pi;
//å°æ°ç¹ç¬¬ïŒäœä»¥éãåãæšãŠ
area = (int)(area * 100);
area = area / 100;
System.out.println("ååŸïŒ" + radius);
System.out.println("é¢ç©ïŒ" + area);
}
}
//å°æ°ç¹ç¬¬ïŒäœä»¥éãåãæšãŠ
area = (int)(area * 100);
area = area / 100;
ããïŒïŒãããšæ¡æ°ã倧ããã«ãšã£ãŠç¡çãããã£ã¹ãã§èœãšã蟌ã¿ããã®äžã§æåŸã«ïŒïŒïŒãå²ãããããããšãæ¡æ°ãæžãã®ãã»ã»ã»
é ããããïŒïŒïŒ
ãã£ã¹ãã¯ãå°æ°ç¹ä»¥äžãåãæšãŠãåŠçãããã®ã§ããããå¯èœã«ãªãã®ãã
ã»ïŒå
äºã€ã®æ°åãå ¥ããæã«ã倧ããæ¹ã®å€ã衚瀺ãããªããã
class Comparison{
public static void main(String[] args){
int a = Integer.parseInt(args[0]);
int b = Integer.parseInt(args[1]);
//倧ããã»ãã®å€ã衚瀺
}
}
ïŒã€ã®ãã¿ãŒã³ã§ãifæãäœã£ãŠã¿ãŸããã
class Comparison{
public static void main(String[] args){
int a = Integer.parseInt(args[0]);
int b = Integer.parseInt(args[1]);
//倧ããã»ãã®å€ã衚瀺
ããããããããif (a > b) {
System.out.println("倧ããã®ã¯" + a + "ã§ãã");
} else if (a < b) {
System.out.println("å°ããã®ã¯" + b + "ã§ãã");
ãããããããã} else {
System.out.println("ïŒã€ã®æ°ã¯åãã§ãã")
}
}
åèã³ãŒã
class Comparison{
public static void main(String[] args){
int a = Integer.parseInt(args[0]);
int b = Integer.parseInt(args[1]);
//倧ããæ¹ã®å€ã衚瀺
if( a > b ){
System.out.println("倧ããã®ã¯" + a + "ã§ã");
} else if( b > a ){
System.out.println("倧ããã®ã¯" + b + "ã§ã");
} else {
System.out.println("åãã§ã");
}
}
}
倱æããïŒå€§ããã®ã衚瀺ããã®ã«ããå°ããã®ã¯ã»ã»ã»ããšããæžãæ¹ãããŠããã
if( a > b ){
System.out.println("倧ããã®ã¯" + a + "ã§ã");
} else if( b > a ){
System.out.println("倧ããã®ã¯" + b + "ã§ã");
} else {
System.out.println("åãã§ã");
}
ifæã䜿ãããšã¯ãã£ãŠããã®ã§ããšãããããä¿®æ£ãå¿ èŠã ã
ã»ïŒå
ã¡ãã»ãŒãžãïŒïŒå衚瀺ãããããã°ã©ã ãäœããªããã
class LoopMessage{
public static void main(String[] args){
//ã¡ãã»ãŒãžã10å衚瀺ïŒwhileæïŒ
}
}
ããããã£ãŠã¿ãã»ã»ã»ã»
class LoopMessage{
public static void main(String[] args){
int i = 1;
//ã¡ãã»ãŒãžã10å衚瀺ïŒwhileæïŒ
while(i <= 10){
System.out.println(i +"åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ");
i ++;
}
}
}
ã©ãã ïŒ
1åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
2åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
3åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
4åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
5åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
6åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
7åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
8åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
9åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
10åç®ïŒããªãŒã©ãŒãã³ã°ãåºããããïŒ
åºããïŒïŒããã£ãã
ã»ïŒå
ã³ãã³ãã©ã€ã³ããå ¥åããæååãããã®ãŸãŸè¡šç€ºã§ããããã°ã©ã ãforæã䜿ã£ãŠè¡šç€ºããªããã
class Echo{
public static void main(String[] args){
//ã³ãã³ãã©ã€ã³ã®å
¥åæååã衚瀺ïŒforæïŒ
}
}
>Java Echo aa bb cc
ãšå ¥ãããããã®ãŸãŸ aa bb ccãšãããã®ãåºãŠããã¯ãã
class Echo{
public static void main(String[] args){
//ã³ãã³ãã©ã€ã³ã®å
¥åæååã衚瀺ïŒforæïŒ
for (int = i; i < ; i){
String moji = Integer.parseInt(args[]);
}
Sysytem.out.println(moji);
}
ã ãã ã»ã»ã»ããããªããargs[]ã䜿ããã°ãªãã»ã»ã»ã»ã
åèã³ãŒã
class Echo{
public static void main(String[] args){
//ã³ãã³ãã©ã€ã³ã®å
¥åæååã衚瀺ïŒforæïŒ
for(int i = 0; i < args.length; i++) {
System.out.println(args[i]);
}
}
}
ãããã»ã»ãªãã»ã©ã
for(int i = 0; i < args.length; i++) {
ãŸã宣èšãšããŠint i = 0;
æ¡ä»¶ãšããŠãargs.lengthã«ãããšãèŠçŽ æ°ã«ãªãã
ããã¯ã€ãŸããç§ãã³ãã³ãã©ã€ã³ã«æžããèŠçŽ ã®æ°ã«ãªãã
ãã®èŠçŽ æ°ãããå°ãªãå Žåã¯ãã®èŠçŽ ïŒæååïŒã衚瀺ãããã
äŸãã°aa bb ccãšæã£ãå Žåã
args.lengthã¯3ã ããŸãi=0ããå§ãŸãã®ã§ãi=0,1,2ãŸã§ã®ïŒã€ãåºåãããããšã«ãªãããã£ãŠãæ¡ä»¶åŒã¯i < args.lengthãšããã¹ããªã®ãããã£ãã
ãããŠããã®äžã®
System.out.println(args[i]);
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