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class Super{ void superMethod(){ System.out.println("superMethod") ; } } class Sub extends Super{ //Æȼ«¤Î¥á¥½¥Ã¥É void subMethod(){ System.out.println("subMethod") ; } //¥ª¡¼¥Ð¡¼¥é¥¤¥É void superMethod(){ System.out.println("¥ª¡¼¥Ð¡¼¥é¥¤¥ÉsuperMethod") ; } } class Test{ public static void main(String[] args){ Super s1 = new Super() ; Super s2 = new Sub() ; Sub s3 = new Sub() ; //¤³¤ì¤Ï¡¢¥³¥ó¥Ñ¥¤¥ë¥¨¥é¡¼ //Sub¥¯¥é¥¹»²¾ÈÊÑ¿ô¤ËÂФ·¤Æ¡¢subMethod()¤ò¸Æ¤Ó½Ð¤¹»ö¤Ï¤Ç¤¤ë¤¬¡¢ //»²¾ÈÀè¤Î¥ª¥Ö¥¸¥§¥¯¥È¤¬¼ÂºÝ¤ÏSuper()¤À¤Ã¤¿¾ì¹ç(¤³¤Î¾ì¹ç)¤Ï¡¢ //Super¥ª¥Ö¥¸¥§¥¯¥È¤Ï¤³¤Î¥á¥½¥Ã¥É¤ËÂФ·¤ÆSub¥¯¥é¥¹¤Î¥á¥½¥Ã¥É¤ò //¸Æ¤Ó½Ð¤¹»ö¤Ï¤Ç¤¤Ê¤¤¡£²¿¸Î¤Ê¤é¡¢Super¥¯¥é¥¹¤Ë¤Ï¡¢subMethod() //¤¬Ìµ¤¤¤¿¤á¡£ // Sub s4 = new Super() ; s1.superMethod() ; s2.superMethod() ; s3.subMethod() ; } } »²¾ÈÊÑ¿ô¤ò»²¾ÈÊÑ¿ô¤ËÂåÆþ¤¹¤ë
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class A{ int a ; A(int i){ a = i ; } } class Test{ public static void main(String[] args){ A a = new A(1) ; A b = a ;//¡ System.out.println(b.a) ; System.out.println(a.a) ; b = new A(2) ;//¢ System.out.println(b.a) ; System.out.println(a.a) ; } } ¡¤Ç¿·¤·¤¤»²¾ÈÊÑ¿ô¤òÀë¸À¤·¡¢»²¾ÈÊÑ¿ô¤òÂåÆþ¤·¤Æ¤¤¤ë¡£¤è¤Ã¤Æ¡¢ºÇ½é¤ÎÃͤÏƱ¤¸»²¾ÈÀè¤Ê¤Î¤Ç¡¢Î¾Êý¤È¤â1¤ò»Ø¤¹¡£
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class Zoo{} class Super{} class Test extends Super{ public static void main(String[] args){ Test t = new Test() ; if(t instanceof Test){ System.out.println("t IS-A Test") ; } if(t instanceof Super){ System.out.println("t IS-A Super") ; } Super s = new Test() ; if(s instanceof Test){ System.out.println("s IS-A Test") ; } //¤³¤Î¥³¡¼¥É¤Ïɽ¼¨¤µ¤ì¤Ê¤¤¡£ //¤¹¤Ê¤ï¤Á¡¢IS-A¥Æ¥¹¥È¤ËÉÔ¹ç³Ê¤Ç¤¢¤ë¡£ Super s2 = new Super() ; if(s2 instanceof Test){ System.out.println("s2 IS-A Test") ; } Zoo z = new Zoo() ; //¥³¥ó¥Ñ¥¤¥ë¤Ç¤¤Ê¤¤ if(z instanceof Test){ System.out.println("z IS-A Test") ; } //¥¹¡¼¥Ñ¡¼¥¯¥é¥¹Object¤Ë¤ª¤±¤ë·ë²Ì¤Ï¾ï¤Ëtrue¤Ë¤Ê¤ë if(z instanceof Object){ System.out.println("z IS-A Object") ; } } } ¥¤¥ó¥¿¥Õ¥§¡¼¥¹¤Ë¤ª¤±¤ëinstanceof¤ÎÎã
interface Inter{} class Sub implements Inter{ } class Test extends Sub{ public static void main(String[] args){ Test t = new Test() ; if(t instanceof Test){ System.out.println("t IS-A Test") ; } if(t instanceof Sub){ System.out.println("t IS-A Sub") ; } if(t instanceof Inter){ System.out.println("t IS-A Inter") ; } if(t instanceof Object){ System.out.println("t IS-A Object") ; } Sub s = new Sub() ; if(s instanceof Test){ System.out.println("s IS-A Test") ; } } } null¤Èinstanceof¤ÎÎã
class Test{ public static void main(String[] args){ Test t = null ; boolean b = null instanceof Test ; System.out.println(b) ; boolean b2 = t instanceof Test ; System.out.println(b) ; } } Åù²ÁÀ±é»»»Ò
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class Test{ public static void main(String[] args){ int a = 3 ; double b = 3.0 ; char c = 'c' ; char d = 'd' ; Test t = new Test() ; Test s = t ; Test u = new Test() ; if(a == b){ System.out.println("a == b") ; } else { System.out.println("a != b") ; } if(c != d){ System.out.println("c != d") ; } else { System.out.println("c == d") ; } if(s == t){ System.out.println("s == t") ; } else { System.out.println("s != t") ; } if(s == u){ System.out.println("s == u") ; } else { System.out.println("s != u") ; } } } »»½Ñ±é»»»Ò
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public static void main(String[] args){ System.out.println(2+1) ;//3 System.out.println(3%2) ;//1 System.out.println(4.0/0) ;//Infinity System.out.println(-4.0/0) ;//-Infinity System.out.println(0.0/0) ;//NaN System.out.println(-4.0%0) ;//NaN //¤³¤ì¤Ï¡¢¥é¥ó¥¿¥¤¥àÎã³° System.out.println(4%0) ; //¤³¤ì¤â¡¢¥é¥ó¥¿¥¤¥àÎã³° System.out.println(4/0) ; } } ʸ»úÎóÏ¢·ë±é»»»Ò
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class Test{ public static void main(String[] args){ String s = "Test" ; System.out.println(s + 3 + 3) ;//Test33 System.out.println(s + (3 + 3)) ;//Test6 System.out.println(3 + 3 + s) ;//6Test System.out.println(3 + (3 + s)) ;//33Test System.out.println("a + b=" + 3 + 3) ;//a + b =33 System.out.println("a + b=" + (3 + 3)) ;//a + b =6 } } ¥¤¥ó¥¯¥ê¥á¥ó¥È¤È¥Ç¥¯¥ê¥á¥ó¥È
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class Test{ public static void main(String[] args){ int a = 0 ; System.out.println(a++) ;//¸åÃÖ·¿¼¡¤Î¸Æ¤Ó½Ð¤·»þ¤Ë¥¤¥ó¥¯¥ê¥á¥ó¥È¤µ¤ì¤ë¡£¡Ö0¡× System.out.println(a) ;//¤³¤³¤Ï¡Ö1¡×¤Èɽ¼¨¤µ¤ì¤ë¡£ System.out.println(a++) ;//¸åÃÖ·¿¼¡¤Î¸Æ¤Ó½Ð¤·»þ¤Ë¥¤¥ó¥¯¥ê¥á¥ó¥È¤µ¤ì¤ë¡£¡Ö1¡× System.out.println(++a) ;//Á°ÃÖ·¿¤³¤Î»þÅÀ¤Ç¥¤¥ó¥¯¥ê¥á¥ó¥È¤µ¤ì¤ë¡£¡Ö3¡× System.out.println(--a) ;//Á°ÃÖ·¿¤³¤Î»þÅÀ¤Ç¥Ç¥¯¥ê¥á¥ó¥È¤µ¤ì¤ë¡£¡Ö2¡× System.out.println(a--) ;//Á°ÃÖ·¿¼¡¤Î¸Æ¤Ó½Ð¤·»þ¤Ë¥Ç¥¯¥ê¥á¥ó¥È¤µ¤ì¤ë¡£¡Ö2¡× System.out.println(a) ;//¤³¤³¤Ï¡Ö1¡×¤Èɽ¼¨¤µ¤ì¤ë¡£ } } ¥·¥Õ¥È±é»»»Ò
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class Test{ public static void main(String[] args){ int a = 0 ; System.out.println(8 >>> 1) ;//4 System.out.println(16 >> 5) ;//0 System.out.println(16 << 33) ;//64 System.out.println(32 << 1) ;//64 } } ¥Ó¥Ã¥È±é»»»Ò
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class Test{ public static void main(String[] args){ int a = 0 ; System.out.println(8 & 5) ;//0 System.out.println(8 | 5) ;//13 System.out.println(8 ^ 5) ;//13 } } ¥Ó¥Ã¥ÈÊä¿ô±é»»»Ò
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class Test{ public static void main(String[] args){ int a = 0 ; System.out.println(~8) ;//-9 } } ¾ò·ï±é»»»Ò
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class Test{ public static void main(String[] args){ int a = 1 ; String s ; s = (a == 0) ? "s == 0" : (a == 1) ? "a == 1" : " a != 0 " ; System.out.println(s) ; } } ûÍíÏÀÍý±é»»»Ò
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class Test{ public static void main(String[] args){ int a = 0 ; int b = 0 ; for(int i = 0 ; i < 4 ; i++){ if( a++ > 1 && ++b > 1){ System.out.println("a=" + a + " b=" + b ) ; } } } } ÈóûÍíÏÀÍý±é»»»Ò
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class Test{ public static void main(String[] args){ int s= 0 ; boolean[] b = {true,false,true,false} ; if(++s > 0 && b[1] | b[0]){ System.out.println("true") ; } else { System.out.println("false") ; } if(b[0] & b[1] | b[2] & b[3] | b[2]){ System.out.println("true") ; } else { System.out.println("false") ; } if(b[0] && b[1] | b[2] & b[3] | b[2]){ System.out.println("true") ; } else { System.out.println("false") ; } } } |
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