java 20121219 1.0.0 -1 javajdkjavajdk2 javaifswitchcifswitchcjavaccharatjdkcharat(): str.chatat(0)str,str.charat(str.length()-1)3 4 voidreturn5 for(i=0; i<6; i+)ni = aa%10; /aa%10aaaaai aa = (int)aa/10; /aa/10aa6 javatouppercasejdk7 umlpublicprivatestaticjava8 javaumljavaabstract finalfinalextendsab class a extends bpublic int age(int year) int age;int a1 = (int)(time/10000); /int)time/100008int a2 = (int)(year/10000); / age = a2 - a1 +1;/ return age;9 interfaceabstractabstractimplementsclass circle implements shapecircleshape10 10math.random()public static void main(string args) circle cir = new circle(9); square squ = new square(4); shape shape; int r; r = (int)(math.random()*2);/math.random()0.00if(r = 0) shape = cir; else shape = squ; shape.testshape(shape); /1.00,201 11 thread setname()start()thread.currentthread().getname()thread.currentthread().getid()threadthread.currentthread().getpriority()thread12 i/ojavai/o17javajava