[java鍩虹]澶嶄範 java涓夊ぇ鐗规€э紝寮傚父锛屾帴鍙ｏ紝String

Posted 2020-12-21

鏍囩锛?a href='http://www.mamicode.com/so/1/extends' title='extends'>extends   瀛楃   sage   搴曞眰瀹炵幇   city   syn   鎵ц   鍒嗛厤   super   

• 缁ф壙
  鍏抽敭瀛梕xtends
  缁ф壙鏄负浜嗕笉鍚岀殑瀹炵幇锛堥緳鐢熶節瀛愶紝鍚勪笉鐩稿悓锛?br> 鍗曠户鎵匡紝涓€涓被鏈€澶氬彧鑳芥湁涓€涓埗绫?br> 闄や簡绉佹湁鐨勫锛屽瓙绫诲彲浠ヨ闂埗绫荤殑鏂规硶銆佸睘鎬с€?br> new杩囩▼涓紝鐖剁被鍏堣繘琛屽垵濮嬪寲锛屽彲閫氳繃super璋冪敤鐖剁被鐩稿簲鐨勬瀯閫犳柟娉曪紝娌℃湁浣跨敤super鐨勬儏鍐典笅锛岃皟鐢ㄧ埗绫荤殑榛樿鏋勯€犳柟娉?br> 闃叉缁ф壙浣跨敤final鍏抽敭瀛?/li>
• 澶氭€?br> 瀛愮被瀵硅薄鍙互璧嬪€肩粰鐖剁被寮曠敤鍙橀噺锛涗絾鏄墽琛岀殑鏃跺€欒皟鐢ㄧ殑鍗存槸瀛愮被鐨勫疄鐜般€?/li>
• 閲嶈浇涓庨噸鍐?br> 閲嶅啓鍙戠敓鍦ㄥ瓙绫伙紝涓昏鏄负浜嗗拰鐖剁被涓嶄竴鏍风殑瀹炵幇;
  閲嶈浇鍙戠敓鍦ㄦ柟娉曚箣闂达紝涓昏鏄负浜嗛€傚簲涓嶅悓鐨勫叆鍙傜被鍨嬨€佹暟閲忋€?br> 閲嶅啓鍙戠敓鍦ㄧ紪璇戞湡闂达紝鑰岄噸杞藉彂鐢熷湪杩愯鏈熼棿銆?/li>
• 绫诲姞杞界殑杩囩▼
  鍔ㄦ€佸姞杞斤紝鐢ㄥ埌鍔犺浇锛屽姞杞界殑鏃跺€欙紝濡傛灉鐖剁被宸茬粡鍔犺浇锛屽垯鐩存帴鍔犺浇锛涘惁鍒欏厛鍔犺浇鐖剁被銆?/li>
• java鍐呭瓨
  鍐呭瓨鍒嗕负鏍堝拰鍫嗭紝鏍堝瓨鏀惧嚱鏁扮殑灞€閮ㄥ彉閲忥紝鑰屽爢瀛樻斁鍔ㄦ€佸垎閰嶇殑瀵硅薄锛岃繕鏈変竴涓唴瀛樺尯锛屽瓨鏀剧被鐨勪俊鎭紝杩欎釜鍖哄湪Java涓О涓烘柟娉曞尯銆備緥濡侫 a = new A(); new A() 鍑虹殑瀵硅薄鍦ㄥ爢锛岃€孉 a 鍙橀噺瀛樺湪鏍堬紱A 鐨勪竴浜涗俊鎭?鏂规硶浠€涔堢殑閮藉湪鏂规硶鍖恒€?br> JVM涓轰簡鎻愬崌鎬ц兘鍜屽噺灏戝唴瀛樺紑閿€锛岄伩鍏嶅瓧绗︿覆鐨勯噸澶嶅垱寤猴紝鍏剁淮鎶や簡涓€鍧楃壒娈婄殑鍐呭瓨绌洪棿锛岃繖灏辨槸鎴戜滑浠婂ぉ瑕佽璁虹殑鏍稿績锛屽嵆瀛楃涓叉睜锛圫tring Pool锛夈€傚瓧绗︿覆姹犵敱String绫荤鏈夌殑缁存姢
• 鎺ュ彛
  鍏抽敭瀛梚nterface,implements ;鍙互瀹炵幇澶氫釜鎺ュ彛锛屼娇鐢ㄩ€楀彿
  鎺ュ彛閲岀殑鏂规硶鍚嶉兘鏄痯ublic鐨勶紝鍐欎笉鍐欎慨楗扮閮戒竴鏍枫€?br> Java8涔嬪墠涓嶈兘鍐欐柟娉曚綋銆侸ava8 鏈変釜渚嬪 鍙互浣跨敤default鍏抽敭瀛楀啓鏂规硶浣擄紱

public interface BaseService {
    default void sayHello(){
        System.out.println("helo");
    }
}
public class BaseServiceImpl implements BaseService {
    
    public static void main(String[] args) {
        BaseService baseService = new BaseServiceImpl();
        baseService.sayHello();
    }
}

• 鐢ㄦ潵鍒ゆ柇涓€涓璞℃槸鍚﹀疄鐜颁簡鏌愭帴鍙ｏ紵
  java浣跨敤instanceof锛宩s 浣跨敤typeof
• 鎶借薄绫?br> 鍏抽敭瀛?abstract ,鍙互琚户鎵匡紝娌℃湁鏋勯€犲嚱鏁般€?br> 閫氬父鎶借薄绫绘惌閰嶆帴鍙ｄ娇鐢紝鎶借薄绫绘彁渚涢粯璁ゅ疄鐜帮紝绫讳技涓巎ava8涔嬪悗鎺ュ彛鐨勬柟娉曞０鏄庣敤default澹版槑鍐欐柟娉曚綋涓€鏍凤紝鑰屾帴鍙ｅ０鏄庡姛鑳斤紱
  渚嬪锛?/li>

public interface BaseService {
    void sayHello();
}
/**
 * 榛樿瀹炵幇鎶借薄绫? */
public abstract class MyService {
    public void sayHello(){
        System.out.println("my hello");
    }
}
public class BaseServiceImpl extends MyService implements BaseService {
    
    public static void main(String[] args) {
        BaseService baseService = new BaseServiceImpl();
        baseService.sayHello();
    }
}

• 寮傚父
  鎵€鏈夌殑寮傚父绫婚兘鏈変竴涓埗绫籘hrowable锛孴hrowable 涓ゅぇ瀛愮被锛堝緱鍔涘共灏嗭級 ErrorException;濡備笅锛?/li>

public class MyException {
    public static void main(String[] args) {
        int s = testExcep();
        System.out.println("杩斿洖鍊硷細"+s);
    }
    private static int testExcep() {
        int a = 0;
        try {
            a = 9/0;
            //return a;  //杩斿洖鍊间负9锛屽幓鎺塺eturn ,a鐨勫€煎湪finally 閲岃淇敼锛屽鏋渇inally 閲屾湁return鍒欒繑鍥?锛屾病鏈塺eturn 灏卞湪杩欓噷鐩存帴杩斿洖锛岄櫎闈炰骇鐢熷紓甯革紝娌℃湁鎵цreturn
        }catch (Exception e){
            System.out.println(e.getMessage());
            a= 7;
            return a; //catch 閲岀殑return浼?finally 閲岀殑return 鎸ゆ帀
        }finally {
            System.out.println("鎵ц");
            a = 8;
            //return a; //鏃犺涔嬪墠鏈夋病鏈塺eturn ,閮戒細鎵цfinally閲岀殑return锛涘鏋渇inally 閲屾病鏈塺eturn ,杩檙eturn 鍦ㄥ摢锛屽氨杩斿洖鏈€杩戠殑鍊硷紱
        }
        return a;
    }
}

Try(杩欓噷鍒涘缓鐨勫璞¤嚜鍔ㄥ叧闂紝姣斿inputStream.){..}catch{...}finally{閲婃斁璧勬簮}

• String ,StringBuffer,StringBuilder
  String绫讳篃鏄笉鍙彉绫伙紝鍗冲璞′竴鏃﹀垱寤猴紝灏辨病鏈夊姙娉曚慨鏀逛簡銆係tring绫讳篃澹版槑涓轰簡final锛屼笉鑳借缁ф壙锛屽唴閮╟har鏁扮粍value涔熸槸final鐨勶紝鍒濆鍖栧悗灏变笉鑳藉啀鍙樹簡
  https://www.cnblogs.com/cold-windy/p/11514977.html 璁插瓧绗︿覆鐨勫瓨鍌?br> StringBuffer绾跨▼瀹夊叏鐨勶紝鑰孲tringBuilder 鏄嚎绋嬩笉瀹夊叏鐨勶紝搴曞眰瀹炵幇閮芥槸char[] ,StringBuffer涔嬫墍浠ョ嚎绋嬪畨鍏紝鏄洜涓洪噸鍐欑殑append()鏂规硶锛宔nsureCapacity锛堬級绛夊姞浜唖ynchronized锛氬涓?/li>

@Override
    public synchronized StringBuffer append(CharSequence s) {
        toStringCache = null;
        super.append(s);
        return this;
 }

搴曞眰瀹炵幇鏄痗har[],鍒濆瀹归噺16锛?br> StringBuilder绾跨▼涓嶅畨鍏紝鍥犱负娌″姞閿併€?/p>

• +鍜?= 鐨勫尯鍒?br> +鍜?= 閮芥槸java缂栬瘧鍣ㄦ敮鎸佺殑杩愮畻绗︼紝浼氳浆鍖栨垚StringBuilder杩涜澶勭悊锛屾墍浠ユ嫾鎺ュ簳灞傞兘鏄娇鐢╝ppend()鏂规硶銆?/li>
• 鏃㈢劧+ 鎴栬€呮槸+= 閮芥槸閫氳繃StringBuilder瀹炵幇鐨勶紝閭ｄ箞杩樻湁蹇呰鍘讳娇鐢⊿tringBuilder鍚楋紵
  濡傛灉鍙槸绠€鍗曠殑鎷兼帴锛屼娇涓嶄娇鐢⊿tringBuilder宸埆涓嶅ぇ銆備絾鏄鏋滄暟閲忓ぇ涓斿惊鐜嫾鎺ョ殑璇濓紝宸窛灏卞緢鏄庢樉锛屽洜涓轰娇鐢⊿tringBuilder灏卞彧闇€瑕佷竴娆″璞★紝鑰屽鏋滀娇鐢? 鎴栬€?= 鐨勮瘽锛岀瓑鍚屼簬姣忓惊鐜竴娆★紝缂栬瘧鍣ㄦ瘡閬囧埌涓€涓?+ 灏眓ew StringBuiler(),鎵€浠ヤ細鑰楄垂澶ч噺鏃堕棿銆?/li>
• 璇村埌string 灏卞繀椤昏皥鐨別quals(str)浠ュ強==锛?br> equals 涓昏鐢ㄦ潵姣旇緝鍐呭锛屽鏋滄槸寮曠敤绫诲瀷鐨勮瘽锛岃繕闇€瑕佹瘮瀵筯ashCode锛岃€?== 涓昏姣旇緝鍩虹鏁版嵁绫诲瀷锛堟瘮鐨勬槸鍐呭瓨鍦板潃锛夈€?br> hashCode鍜宔quals鏂规硶鑱旂郴瀵嗗垏锛屽涓や釜瀵硅薄锛屽鏋渆quals鏂规硶杩斿洖true锛屽垯hashCode涔熷繀椤讳竴鏍枫€傚弽涔嬩笉瑕佹眰锛宔qual鏂规硶杩斿洖false鏃讹紝hashCode鍙互涓€鏍凤紝涔熷彲浠ヤ笉涓€鏍凤紝浣嗗簲璇ュ敖閲忎笉涓€鏍枫€俬ashCode鐨勯粯璁ゅ疄鐜颁竴鑸槸灏嗗璞＄殑鍐呭瓨鍦板潃杞崲涓烘暣鏁帮紝瀛愮被濡傛灉閲嶅啓浜唀quals鏂规硶锛屼篃蹇呴』閲嶅啓hashCode銆?/li>
• 瀛楄妭缂栫爜

Charset charset = Charset.forName("utf-8");//import java.nio.charset.Charset;