J2EE部分packagetest;publicclassTest{publicstaticvoidmain(String[]args){精品文檔放心下載intk=0;intret=++k+k+++++k+k;感謝閱讀//ret的值為多少System.err.println(ret);}}packagetest;publicclassTest{publicstaticvoidmain(String[]args){感謝閱讀inti1=10,i2=10;System.err.println("i1+i2="+i1+i2);感謝閱讀System.err.println("i1-i2="+i1-i2);精品文檔放心下載System.err.println("i1*i2="+i1*i2);謝謝閱讀System.err.println("i1/i2="+i1/i2);精品文檔放心下載}}packagetest;publicclassTest{publicvoidmyMethod(Stringstr){精品文檔放心下載System.err.println("string");謝謝閱讀}publicvoidmyMethod(Objectobj){精品文檔放心下載System.err.println("object");謝謝閱讀}publicstaticvoidmain(String[]args){謝謝閱讀Testt=newTest();t.myMethod(null);}}..packagetest;importjava.util.Date;publicclassTest{publicstaticvoidmain(String[]args){感謝閱讀Datedate=newDate();System.err.println(date.getMonth()+""+date.getDate());謝謝閱讀}}packagetest;publicclassTest{publicstaticvoidmain(String[]args){感謝閱讀doubleval=11.5;System.err.println(Math.round(val));謝謝閱讀System.err.println(Math.floor(val));感謝閱讀System.err.println(Math.ceil(val));精品文檔放心下載}}packagetest;publicclassTestextendsBase{精品文檔放心下載publicstaticvoidmain(String[]args){謝謝閱讀Baseb=newTest();b.method();Testt=newTest();t.method();}@Overridepublicvoidmethod(){System.err.println("test");謝謝閱讀}}classBase{publicvoidmethod()throwsInterruptedException{精品文檔放心下載System.err.println("base");謝謝閱讀}}..packagetest;publicclassTestextendsBase{感謝閱讀publicstaticvoidmain(String[]args){感謝閱讀newTest().method();}publicvoidmethod(){System.err.println(super.getClass().getName());精品文檔放心下載System.err.println(this.getClass().getSuperclass().getName());感謝閱讀}}classBase{}？packagetest;publicclassTest{publicstaticvoidmain(String[]args){謝謝閱讀Stringstr1=newString("abc");精品文檔放心下載Stringstr2=newString("abc");感謝閱讀System.err.println(str1.equals(str2));感謝閱讀StringBuffersb1=newStringBuffer("abc");感謝閱讀StringBuffersb2=newStringBuffer("abc");精品文檔放心下載System.err.println(sb1.equals(sb2));精品文檔放心下載}}packagetest;publicclassTest{publicstaticvoidmain(String[]args){感謝閱讀System.err.println(newTest().method1());謝謝閱讀System.err.println(newTest().method2());謝謝閱讀}publicintmethod1(){intx=1;try{returnx;}finally{++x;}}publicintmethod2(){..intx=1;try{returnx;}finally{return++x;}}}packagetest;publicclassTest{publicstaticvoidmain(String[]args){謝謝閱讀System.err.println(method());精品文檔放心下載}publicstaticbooleanmethod(){謝謝閱讀try{returntrue;}finally{returnfalse;}}}和packagetest;publicclassTest{publicstaticvoidmain(String[]args){感謝閱讀}publicsynchronizedvoidm1(){感謝閱讀}publicstaticsynchronizedvoidm2(){謝謝閱讀}}..packagetest;publicclassTest{publicstaticvoidmain(String[]args){精品文檔放心下載Integeri1=127;Integeri2=127;System.err.println(i1==i2);精品文檔放心下載i1=128;i2=128;System.err.println(i1==i2);精品文檔放心下載}}packagetest;publicclassTest{publicstaticvoidmain(String[]args){謝謝閱讀Stringstr1="a";Stringstr2="a";Stringstr3=newString("a");感謝閱讀System.err.println(str1==str2);感謝閱讀System.err.println(str1==str3);感謝閱讀str3=/r/ern();System.err.println(str1==str3);感謝閱讀}}packagetest;publicclassTest{publicstaticvoidmain(String[]args){精品文檔放心下載System.err.println(12-11.9==0.1);精品文檔放心下載}}..packagetest;importjava.math.BigInteger;謝謝閱讀publicclassTest{publicstaticvoidmain(String[]args){精品文檔放心下載BigIntegerone=newBigInteger("1");感謝閱讀BigIntegertwo=newBigInteger("2");精品文檔放心下載BigIntegerthree=newBigInteger("3");謝謝閱讀BigIntegersum=newBigInteger("0");感謝閱讀sum.add(one);sum.add(two);sum.add(three);System.out.println(sum.toString());精品文檔放心下載}}感謝閱讀packagetest;importjava.util.HashSet;importjava.util.Iterator;感謝閱讀importjava.util.Set;publicclassTest{publicstaticvoidmain(String[]args){謝謝閱讀Set<String>set=newHashSet<String>();精品文檔放心下載set.add("one");set.add("two");set.add("three");set.add("four");set.add("five");for(Iterator<String>it=set.iterator();it.hasNext();){謝謝閱讀System.err.println(it.next());精品文檔放心下載}}}..publicclassTest{publicstaticvoidmain(String[]args){謝謝閱讀System.err.println(args.length);精品文檔放心下載}}A.nullB.0C.TestD.Exceptioninthread"main"java.lang.NullPointerException精品文檔放心下載感謝閱讀publicclassTest{publicTestinstance=null;謝謝閱讀publicstaticTestgetInstance(){謝謝閱讀if(instance==null){instance=newTest();returninstance;}}}謝謝閱讀謝謝閱讀..、、8i1+i2=1010語法錯誤i1*i2=100i1/i2=1、、string519、、12test11.0test12.0、、test.Testtruetest.Basefalse、、1A:synchronized是某個類的范圍，感謝閱讀2synchronizedstaticcSync{}防止多個線程同感謝閱讀false時訪問這個類中的synchronizedstatic方謝謝閱讀法。它可以對類的所有對象實例起作用。B:synchronized是某實例的范圍，synchronized防止多個線程同時謝謝閱讀訪問這個實例中的synchronized方法。、、truetruefalsefalsetrue、、false0、、twoBfiveonethreefour、getInstance無默認返回值instance必須是static、packagetest;importjava.io.File;publicclassTest{publicstaticvoidmain(String[]args){感謝閱讀..newTest().read("D:/test","");感謝閱讀}publicvoidread(Stringpath,Stringtab){感謝閱讀Filefile=newFile(path);感謝閱讀File[]childFiles=file.listFiles();精品文檔放心下載for(inti=0;childFiles!=null&&i<childFiles.length;i++){謝謝閱讀System.err.println(tab+childFiles[i].getName());精品文檔放心下載if(childFiles[i].isDirectory()){感謝閱讀read(childFiles[i].getPath(),tab+"\t");精品文檔放心下載}}}}、packagetest;importjava.util.Arrays;importjava.util.Comparator;感謝閱讀importjava.util.Scanner;publicclassTest{publicstaticvoidmain(String[]args){謝謝閱讀Scannerin=newScanner(System.in);感謝閱讀//注意這里的數組，不是int的Integer[]arr=newInteger[10];感謝閱讀for(inti=0;i<10;i++){精品文檔放心下載arr[i]=in.nextInt();}Arrays.sort(arr,newComparator<Integer>(){謝謝閱讀@Overridepublicintcompare(Integero1,Integero2){謝謝閱讀if(o1/r/