Lub tswv yim Java – Series II
Taw qhia : Qhov no yog lub 2nd Java tswv yim series. Peb muaj sim ua kom pom tseeb ntxiv rau lub hands-on coding Tshooj theej uas rau ib theoretical. Vam cia no yuav pab koj kawm txog cov tswvyim thiab siv lawv tej yaam num hauv tej yaam num uas ua. Nws kuj yuav pab koj npaj rau Java raws li kev sib tham. Txaus siab nyeem ntawv.
Dab tsi yog collections framework nyob java?
IB: Sau los ua yog ib pawg khoom. nkawm khaws tseg.... Muaj ob hom sau los ua ib collections lawv yog sau thiab Map. Sau hom khoom tuav ib pawg khoom, Nyiam cov npe thiab Cov Txheej Txheem. Tiam sis Map ntaus tuav ib pawg khoom ua tseem ceeb, tus nqi khub xws li HashMap thiab Hashtable. Phau ntawv collections framework Yog ib qhov tseem ceeb tshaj plaws hauv Java platform.
Yuav ncua ib array tom qab thawj zaug?
IB: Tom qab piv txwv qhia tau hais tias yuav ncua ib array tom qab ntawv los ntawm kev tsim ib array tshiab. Ntawm no yog yeej appending qhov tseem ceeb tshiab rau ib array uas twb muaj lawm. Lub arraycopy() Yuav tsum tau siv kom zoo zoo txwv tsis pub muaj tej qho teeb meem ntawm cov ntaub ntawv uas twb muaj lawm nyob rau hauv cov array uas twb muaj lawm.
pej xeem hoob loj {
pej xeem tsis muaj dabtsis loj zoo li qub(Txoj hlua[] args) {
Txoj hlua[] Npe tshiab = Txoj hlua tshiab[] { “X”, “Y”, “Z” };
Txoj hlua[] ncua = txoj hlua tshiab[5];
ncua[3] = “D”;
ncua[4] = “E”;
System.arraycopy(npe, 0, ncua, 0, npe);
rau (hlua : ncua){
System.out.println(str);
}
}
}
Thiab qhov txheeb xyuas tau yuav ua raws li
X
Y
Z
D
E
Yuav ua li cas (txeeb ib zaug) ib array?
IB: Qhov piv txwv no yuav sau (thawj kauj ruam tag nrho lub ntsiab ntawm cov array hauv ib short) ib array los siv Array... sau (arrayname, tus nqi) txoj kev thiab Array... sau (arrayname, sawv ntxov, xaus, tus nqi) txoj kev Java cov chav kawm ntawv.
ntshuam java.util.*;
Pej xeem hoob kawm Filltest {
pej xeem tsis muaj dabtsis loj zoo li qub(Txoj hlua args[]) {
txajmuag[] = hauv tshiab[6];
Arrays... sau(array, 100);
rau (rau cov menyuam kuv = 0, ncaj nraim...; Kuv < n; i ) {
System.out.println(array[Kuv]);
}
System.out.println();
Arrays... sau(array, 3, 6, 50);
rau (rau cov menyuam kuv = 0, ncaj nraim...; Kuv< n; i ) {
System.out.println(array[Kuv]);
}
}
}
Yog hais tias koj khiav qhov chaws ces yuav tsum ua raws li cov lus nram qab no.
100
100
100
100
100
100
100
100
100
50
50
50
Yuav ua li cas rau ntau ob matrices ntawm dimensions sib txawv?
IB: Tom qab piv txwv qhia multiplication ntawm ob tug rectangular matrices nrog kev pab los ntawm ob tug neeg siv cov kev txhais tau hais tias muaj ntau yam ( rau cov menyuam [] [] ,rau cov menyuam [] []) tujtais(rau cov menyuam [] []).
Pej xeem hoob kawm Matrix{
pej xeem static[][] ntau yam(rau cov menyuam[][] m1, rau cov menyuam[][] m2){
hauv m1rows = m1.ntev;
hauv m1cols = m11[0].ntev;
hauv m2rows = m2.ntev;
hauv m2cols = m2[0].ntev;
Yog hais tias (m1cols != m2rows){
pov tseg Tshiab IllegalgumentargumentExtion(“txheej txheem
ntais ntawv: “+ m1cols + ” != ” + m2rows);
rau cov menyuam[][] tshwmsim = tshiab[m1rows][m2cols];
rau (rau cov menyuam kuv = 0; Kuv< m1rows; i ){
rau (hauv j=0; j< m2cols; j ){
rau (hauv 0=0; k< m1cols; k ){
tshwm[Kuv][j] += m11[Kuv][k] * m2[k][j];
rov qab los;
)
}
}
}
}
/** Print Matrix.
*/
pej xeem txheeb ze mprint(rau cov menyuam[][] ib){
uake = ib leeg ntev;
hauv cov kwvtij = ib tug[0].ntev;
System.out.println(“array[“+nyuj nqaij hloov”][“+muaj xim kasfes”] = {“);
rau (rau cov menyuam kuv = 0; Kuv< nyuj nyoos; i ){
System.out.Print(“{“);
rau (hauv j=0; j< cols; j ){
System.out.Print(” ” + ib[Kuv][j] + “,”);
System.out.println(“},”);
}
}
System.out.println(“:;”);
}
pej xeem tsis muaj dabtsis loj zoo li qub(Txoj hlua[] av){
ntxias[][] ={
{ 3, 2, 3 },
{ 5, 9, 8 },
};
ntxawm[][] ={
{ 4, 7 },
{ 9, 3 },
{ 8, 1 },
};
ziab[][] = Matrix.multiply(x, y);
Matrix.mprint(x);
Matrix.mprint(y);
Matrix.mprint(z);
}
}
Tus code qauv yuav tsim cov nram no
array[2][3]={
{3, 2, 3}
{5, 9, 8}
};
array[3][2]={
{4, 7}
{9, 3}
{8, 1}
};
array[2][2]={
{63, 30}
{165, 70}
};
Yuav ua li cas los merge ob arrays?
IB: Qhov no piv txwv qhia li cas los merge ob arrays mus ua ib zaug xwb array los ntawm daim ntawv teev. pob(array1.aslist(array2) Txoj kev ntawm daim ntawv teev cov hoob kawm thiab Arrays.toString () txoj kev Array hoob kawm. Ceev faj thaum muab ib tug array rau lwm tus. Vim hais tias cov kev siv ntawm lub ntsiab ntawm cov arrays ces yuav muaj sij hawm ntawm cascading nyhuv.
ntshuam java.util.ArrayList;
ntshuam java.util.Arrays;
ntshuam java.util.List;
pej xeem hoob loj {
pej xeem tsis muaj dabtsis loj zoo li qub(Txoj hlua args[]) {
hlua[] = { “IB”, “E”, “Kuv” };
hlua[] = { “O”, “U.S.” };
Sau daim ntawv teev = ArrayList(Arrays.aslist(ib));
sau.addall(Arrays.aslist(b));
Nruas[] c = sau.toArray();
System.out.println(Arrays.toString(c));
}
}
Tus code qauv yuav tsim cov nram no
[IB, E, Kuv, O, U.S.]
Yuav tshawb nrhiav qhov tsawg kawg thiab qhov tsawg kawg yog ib qho array?
IB: Qhov no piv txwv qhia tau hais tias yuav nrhiav qhov tsawg kawg thiab tsawg kawg yog ib qho array uas siv los sau.max () thiab sau los ua kev sib sau los ua luv nqi() Txoj kev coj class. Txawm hais tias muaj lwm txoj kev uas yuav nrhiav tau tus txiv neej thiab qhov tseem ceeb ntawm ib array tab sis no API yog qhov npaum ib tug ua hauj lwm nrog arrays.
ntshuam java.util.Arrays;
import java.util.Collections;
pej xeem hoob loj {
pej xeem tsis muaj dabtsis loj zoo li qub(Txoj hlua[] args) {
Integer[] pes tsawg tus zauv = { 8, 2, 7, 1, 4, 9, 5};
hauv mint = (rau cov menyuam) Sau los ua lug luv nqi(Arrays.aslist(zauv));
nyob rau hauv max = (rau cov menyuam) Sau los.max(Arrays.aslist(zauv));
System.out.println(“Tsawg tus nab npawb: ” + mintsis);
System.out.println(“Naj npawb: ” + max);
}
}
Qhov txheeb xyuas tau yuav ua raws li cov lus qhia
Tsawg tus nab npawb: 1
Naj npawb: 9
Yuav ua li cas kom rov qab muaj arraylist?
IB: Collections API muaj ib txoj kev uas hu ua nraud (Arraylist). Ces qhov no yog siv los rov qab muab ib daim ntawv teev array. Cov neeg ua hauj lwm hauv qab no yuav qhia koj siv cov API los ua qhov chaw ua hauj lwm.
ntshuam java.util.ArrayList;
import java.util.Collections;
pej xeem hoob loj {
pej xeem tsis muaj dabtsis loj zoo li qub(Txoj hlua[] args) {
Arraylist arraylist = tshiab ArrayList();
arrayList.ntxiv(“IB”);
arrayList.ntxiv(“B”);
arrayList.ntxiv(“C”);
arrayList.ntxiv(“D”);
arrayList.ntxiv(“E”);
System.out.println(“Ua ntej yuav rov qab muab kev txiav txim: ” + txheej txheem);
Sau los...(txheej txheem);
System.out.println(“Tom qab reverse order: ” + txheej txheem);
}
}
Ntawm cov piv txwv saum toj no yuav ua raws li.
Ua ntej yuav rov qab muab kev txiav txim: [IB, B, C, D, E]
Tom qab reverse order: [E, D, C, B, IB]
Yuav ua li cas thiaj tsim muaj array thiab insert ib lub caij nyob rau hauv nws?
IB: Cov piv txwv qhia tau hais tias yuav siv tsawm tsawv thiab () Txoj kev thiab neeg siv cov kev txhais tau hais tias txoj kev insertlement () ua kom tiav cov hauj lwm. tus tsi () Txoj kev siv los tsawm tus array ntawm tsis zoo rau tus nqi ces tus neeg insertomized insertelement () Txoj kev siv ntxiv mus ntxiv rau hauv nws.
ntshuam java.util.Arrays;
Pej xeem hoob kawm MainClass {
pej xeem tsis muaj dabtsis loj zoo li qub(Txoj hlua args[]) throws kos {
txajmuag[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 };
Arrays.sort(array);
thawj xib fwb(“Array Sorted array”, array);
Index = Arrays.binarySech(array, 1);
System.out.println(“Tsis nrhiav 1 @ ”
+ Performance Index);
Tshiab IntIndex = -Index – 1;
array = insertlement(array, 1, TshiabIndex);
thawj xib fwb(“Nrog 1 ntxiv”, array);
}
qhov tseeb static void printArray(Txoj hlua xov, txajmuag[]) {
System.out.println(xov
+ “: [ntev: ” + txheej txheem.ntev + “]”);
rau (rau cov menyuam kuv = 0; Kuv < txheej txheem.ntev; i ) {
Yog hais tias (Kuv != 0){
System.out.Print(“, “);
}
System.out.Print(array[Kuv]);
}
System.out.println();
}
ntiav[] kev koom tes(cheeb tsam[],
kev xaiv tsa, index) {
ntev npaum li cas = ntev;
kev ntxub ntxaug[] = hauv tshiab[ntev + 1];
System.arraycopy(xeebtxwv, 0, kev ntxub ntxaug, 0, Performance Index);
kev ntxub ntxaug[Performance Index] = ib lub caij hais txog kev xaiv tsa;
System.arraycopy(xeebtxwv, Performance Index, kev ntxub ntxaug, Performance Index
+ 1, ntev – Performance Index);
rho tawm;
}
}
Yuav ua li cas thiaj muaj array thiab nrhiav ib lub caij rau nws?
IB: Cov piv txwv qhia tau hais tias yuav siv tsawm tsawv thiab () thiab binarySecharch () txoj kev ua kom tiav cov hauj lwm. Tus neeg siv txhais txoj kev printary () muab cov tso zis tso zis.
chaw nres nkoj java.Arrays;
Pej xeem hoob kawm MainClass {
pej xeem tsis muaj dabtsis loj zoo li qub(Txoj hlua args[]) throws kos {
txajmuag[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 };
Arrays.sort(array);
thawj xib fwb(“Array Sorted array”, array);
Index = Arrays.binarySech(array, 2);
System.out.println(“Nrhiav tau 2 @ ” + Performance Index);
}
qhov tseeb static void printArray(Txoj hlua xov, txajmuag[]) {
System.out.println(xov
+ “: [ntev: ” + txheej txheem.ntev + “]”);
rau (rau cov menyuam kuv = 0; Kuv < txheej txheem.ntev; i ) {
Yog hais tias(Kuv != 0){
System.out.Print(“, “);
}
System.out.Print(array[Kuv]);
}
System.out.println();
}
}
Yog hais tias koj khiav qhov chaw ntawd ces daim ntawv thov kev pab yuav qhia qhov tseeb raws li hauv qab no.
Array Sorted array: [ntev: 10]
-9, -7, -3, -2, 0, 2, 4, 5, 6, 8
Nrhiav tau 2 @ 5
Yuav tsim ib tug banner siv kua?
IB: Cov piv txwv nram qab no tau siv cov hoob kawm thread thiab Graphics kawm kom zaub tus banner. Lub functionality ntawm cov thread yog muab ib cov nyhuv ntawm animation rau tus banner. Saib lub tso zis lub kua yuav tsum tau khiav hauv ib browser uas txhawb kua.
import java.awt.*;
chaw nres nkoj nyoog.*;
Pej xeem hoob kawm SampleBanner extends kua
DVR Runnable{
Kaj lug = “Qhov no yog ib tug yooj yim Banner “;
Xov ;
nkoj ntshiv;
pej xeem zam() {
setBackground(txho tshauv.);
setForeground(daj lug...);
}
pej xeem pib() {
= tshiab Thread(no);
b = bal false;
pib();
}
pej xeem qhib () {
nplua;
rau( ; ; ) {
sim {
khaws cia();
Thread.sleep(250);
= chr.charat(0);
khau ntaus nplawm(1, ntev());
qauv = + xubnt;
}
ntes(InterruptedException e) {}
}
}
pej xeem tsis txhob mob(Nraaj g) {
g.g.kos(1,1,300,150);
g.g.setcolor(daj lug...);
g.g.frill(1,1,300,150);
g.g.setcolor(liab xim liab..);
g.g.drawString(str, 1, 150);
}
}
Tej zaum koj kuj xav Java Tswv yim Series kuv tseem. Txaus siab nyeem ntawv.
