最新JAVA编程题全集（50题及答案）

} } }

************************************************************************************************************************************************************** BinarySearch

import java.util.Comparator;

public class BinarySearch {

public static > int binarySearch(T[] a, T x, Comparator comparator) { if (a == null) {

throw new IllegalArgumentException(\被查找数组为null！\); } else if (x == null) {

throw new IllegalArgumentException(\被查询元素为null！\); }

int left = 0;

int right = a.length - 1;

while (left <= right) {

int middle = (left + right) / 2; if (comparator != null) {

if (comparator.compare(x, a[middle]) == 0) return middle;

if (comparator.compare(x, a[middle]) > 0) left = middle + 1; else

right = middle - 1; }

else { if(x.compareTo(a[middle])==0) return middle;

if(x.compareTo(a[middle])>0) left = middle + 1;

else right = middle - 1; } }

return -1; }

public static void main(String[] args) { Student[] a = new Student[4];

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a[0] = (new Student(3, \)); a[1] = (new Student(5, \)); a[2] = (new Student(7, \)); a[3] = (new Student(9, \));

Student x = new Student(7, \);// 设定要查找的数

int position = binarySearch(a, x, new StudentComparator()); System.out.println(x + \在数组中的位置是\ + position);

} }

Student

import java.util.TreeSet; import java.util.Iterator;

public class Student implements Comparable { private int id;

private String name;

public Student (int id, String name) { this.id = id;

this.name = name; }

public void setId (int id) { this.id = id; }

public void setName (String name) { this.name = name; }

public int getId () { return id; }

public String getName () { return name; }

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/* Student 类的字符串表达式，形如： * 2 张三 */

public String toString () {

return (id + \ }

/* 实现 Comparable 接口中的 compareTo 方法， * 通常大于时返回一个正数，小于时返回一个负数， * 等于时返回零，具体情况可以自行决定。

********************************************************* * 这里我根据 id 号的大小进行了比较。由于 TreeSet * 会根据 compareTo 的结果来排序，因此输出结果 * 应该是按照 id 号从小到大排序的。

* 如果要根据姓名进行排序，只需对这个方法进行相应的修改。*/

public int compareTo (Student arg) { if (id > arg.id) return 1; else if (id == arg.id) return 0; else

return -1; }

/* 以下为主方法，输出结果是： * 3 John * 5 Tom * 7 Alice * 9 David

* 可以看到不同于输入顺序， * TreeSet 已经将其排序了。*/

public static void main (String args[]) {

TreeSet tset = new TreeSet(); tset.add(new Student(5, \ tset.add(new Student(3, \ tset.add(new Student(9, \ tset.add(new Student(7, \

Iterator itor = tset.iterator(); while (itor.hasNext()) {

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System.out.println(itor.next().toString()); } } }

StudentComparator

import java.util.Comparator; /**

* Student 比较器 */

public class StudentComparator implements Comparator {

@Override

public int compare(Student s1, Student s2) {

if(s1.getId()>s2.getId()) return 1;

else if(s1.getId()==s2.getId()) return 0; else

return -1; } }

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package test1; /**

* Title: Hello Java World

* Description: 简单的Java程序,只显示一个信息。 * filename: HelloWorld.java */

public class HelloWorld {

public static void main(String[] args) { System.out.println(\ } }

package test2; /**

* Title: Java语言流程演示

* Description: 演示Java中几种常用的流程控制操作 * Filename: flowDome.java */

public class flowDemo{

public static void main(String[] arges){ int iPara1,iPara2,iEnd; if(arges.length!=3) {

System.out.println(\ System.out.println(\比较条件1，数字类型\ System.out.println(\比较条件2，数字类型\ System.out.println(\：循环次数\

System.out.println(\ return; }else{

iPara1 = Integer.parseInt(arges[0]); iPara2 = Integer.parseInt(arges[1]); iEnd = Integer.parseInt(arges[2]); }

//if语句

if(iPara2>iPara1) {

System.out.println(\条件满足！\

System.out.println(\第2个数比第1个数大！\

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