实例-Java 数组

原创 于 2015-05-06 19:43:24 发布 · 148 阅读 · 0 ·
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数组排序及元素查找
/*
 author by lian_le
 文件名：MainClass.java 
 */

import java.util.Arrays;

public class MainClass {
   public static void main(String args[]) throws Exception {
      int array[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 };
      Arrays.sort(array);
      printArray("数组排序结果为", array);
      int index = Arrays.binarySearch(array, 2);
      System.out.println("元素 2  在第 " + index + " 个位置");
   }
   private static void printArray(String message, int array[]) {
      System.out.println(message
      + ": [length: " + array.length + "]");
      for (int i = 0; i < array.length; i++) {
         if(i != 0){
            System.out.print(", ");
         }
         System.out.print(array[i]);                     
      }
      System.out.println();
   }
}

结果：

数组排序结果为: [length: 10] -9, -7, -3, -2, 0, 2, 4, 5, 6, 8
元素 2 在第 5 个位置
数组添加元素
/*
 author by lian_le
 文件名：MainClass.java 
 */

import java.util.Arrays;

public class MainClass {
   public static void main(String args[]) throws Exception {
      int array[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 };
      Arrays.sort(array);
      printArray("数组排序", array);
      int index = Arrays.binarySearch(array, 1);
      System.out.println("元素 1 所在位置（负数为不存在）："
      + index);  
      int newIndex = -index - 1;
      array = insertElement(array, 1, newIndex);
      printArray("数组添加元素 1", array);
   }
   private static void printArray(String message, int array[]) {
      System.out.println(message
      + ": [length: " + array.length + "]");
      for (int i = 0; i < array.length; i++) {
         if (i != 0){
            System.out.print(", ");
         }
         System.out.print(array[i]);         
      }
      System.out.println();
   }
   private static int[] insertElement(int original[],
   int element, int index) {
      int length = original.length;
      int destination[] = new int[length + 1];
      System.arraycopy(original, 0, destination, 0, index);
      destination[index] = element;
      System.arraycopy(original, index, destination, index
      + 1, length - index);
      return destination;
   }
}
获取数组长度
public class Main {
   public static void main(String args[]) {
      String[][] data = new String[2][5];
      System.out.println("第一维数组长度: " + data.length);
      System.out.println("第二维数组长度: " + data[0].length);
   }
}
第一维数组长度: 2 
第二维数组长度: 5
数组反转
/*
 author by lian_le
 文件名：Main.java
 */

import java.util.ArrayList;
import java.util.Collections;

public class Main {
   public static void main(String[] args) {
      ArrayList arrayList = new ArrayList();
      arrayList.add("A");
      arrayList.add("B");
      arrayList.add("C");
      arrayList.add("D");
      arrayList.add("E");
      System.out.println("反转前排序: " + arrayList);
      Collections.reverse(arrayList);
      System.out.println("反转后排序: " + arrayList);
   }
}

结果：

反转前排序: [A, B, C, D, E] 
反转后排序: [E, D, C, B, A]
数组输出
public class Welcome {
   public static void main(String[] args){
      String[] greeting = new String[3];
      greeting[0] = "This is the greeting";
      greeting[1] = "for all the readers from";
      greeting[2] = "Java Source .";
      for (int i = 0; i < greeting.length; i++){
         System.out.println(greeting[i]);
      }
   }
}

结果：

This is the greeting
For all the readers From
Java source .
数组获取最大和最小值
import java.util.Arrays;
import java.util.Collections;

public class Main {
   public static void main(String[] args) {
      Integer[] numbers = { 8, 2, 7, 1, 4, 9, 5};
      int min = (int) Collections.min(Arrays.asList(numbers));
      int max = (int) Collections.max(Arrays.asList(numbers));
      System.out.println("最小值: " + min);
      System.out.println("最大值: " + max);
   }
}

结果：

最小值: 1
最大值: 9
数组合并
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {
   public static void main(String args[]) {
      String a[] = { "A", "E", "I" };
      String b[] = { "O", "U" };
      List list = new ArrayList(Arrays.asList(a));
      list.addAll(Arrays.asList(b));
      Object[] c = list.toArray();
      System.out.println(Arrays.toString(c));
   }
}

结果：

[A, E, I, O, U]
数组填充
import java.util.*;

public class FillTest {
   public static void main(String args[]) {
      int array[] = new int[6];
      Arrays.fill(array, 100);
      for (int i=0, n=array.length; i < n; i++) {
         System.out.println(array[i]);
      }
      System.out.println();
      Arrays.fill(array, 3, 6, 50);
      for (int i=0, n=array.length; i< n; i++) {
         System.out.println(array[i]);
      }
   }
}

结果：

100
100
100
100
100
100

100
100
100
50
50
50
数组扩容
public class Main {
   public static void main(String[] args) {
      String[] names = new String[] { "A", "B", "C" };
      String[] extended = new String[5];
      extended[3] = "D";
      extended[4] = "E";
      System.arraycopy(names, 0, extended, 0, names.length);
      for (String str : extended){
         System.out.println(str);
      }
   }
}

结果：

A
B
C
D
E
数组排序及查找
import java.util.Arrays;

public class MainClass {
    public static void main(String args[]) throws Exception {
        int array[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 };
        Arrays.sort(array);
        printArray("Sorted array", array);
        int index = Arrays.binarySearch(array, 2);
        System.out.println("Found 2 @ " + index);
   }
   private static void printArray(String message, int array[]) {
        System.out.println(message
        + ": [length: " + array.length + "]");
        for (int i = 0; i < array.length; i++) {
            if(i != 0){
                System.out.print(", ");
            }
            System.out.print(array[i]);                     
        }
        System.out.println();
    }
}

结果：

Sorted array: [length: 10]
-9, -7, -3, -2, 0, 2, 4, 5, 6, 8
Found 2 @ 5
删除数组元素
import java.util.ArrayList;

public class Main {
   public static void main(String[] args)  {
      ArrayList objArray = new ArrayList();
      objArray.clear();
      objArray.add(0,"第 0 个元素");
      objArray.add(1,"第 1 个元素");
      objArray.add(2,"第 2 个元素");
      System.out.println("数组删除元素前："+objArray);
      objArray.remove(1);
      objArray.remove("0th element");
      System.out.println("数组删除元素后："+objArray);
   }
}

结果：

数组删除元素前：[第 0 个元素, 第 1 个元素, 第 2 个元素]
数组删除元素后：[第 0 个元素, 第 2 个元素]
数组差集

import java.util.ArrayList;

public class Main {
   public static void main(String[] args)  {
      ArrayList objArray = new ArrayList();
      ArrayList objArray2 = new ArrayList();
      objArray2.add(0,"common1");
      objArray2.add(1,"common2");
      objArray2.add(2,"notcommon");
      objArray2.add(3,"notcommon1");
      objArray.add(0,"common1");
      objArray.add(1,"common2");
      objArray.add(2,"notcommon2");
      System.out.println("array1 的元素" +objArray);
      System.out.println("array2 的元素" +objArray2);
      objArray.removeAll(objArray2);
      System.out.println("array1 与 array2 数组差集为："+objArray);
   }
}

结果：

array1 的元素[common1, common2, notcommon2]
array2 的元素[common1, common2, notcommon, notcommon1]
array1 与 array2 数组差集为：[notcommon2]
数组交集
import java.util.ArrayList;

public class Main {
   public static void main(String[] args)  {
      ArrayList objArray = new ArrayList();
      ArrayList objArray2 = new ArrayList();
      objArray2.add(0,"common1");
      objArray2.add(1,"common2");
      objArray2.add(2,"notcommon");
      objArray2.add(3,"notcommon1");
      objArray.add(0,"common1");
      objArray.add(1,"common2");
      objArray.add(2,"notcommon2");
      System.out.println("array1 数组元素："+objArray);
      System.out.println("array2 数组元素："+objArray2);
      objArray.retainAll(objArray2);
      System.out.println("array2 & array1 数组交集为："+objArray);
   }
}

结果：

array1 数组元素：[common1, common2, notcommon2]
array2 数组元素：[common1, common2, notcommon, notcommon1]
array2 & array1 数组交集为：[common1, common2]
在数组中查找指定元素

import java.util.ArrayList;

public class Main {
   public static void main(String[] args)  {
      ArrayList objArray = new ArrayList();
      ArrayList objArray2 = new ArrayList();
      objArray2.add(0,"common1");
      objArray2.add(1,"common2");
      objArray2.add(2,"notcommon");
      objArray2.add(3,"notcommon1");
      objArray.add(0,"common1");
      objArray.add(1,"common2");
      System.out.println("objArray 的数组元素："+objArray);
      System.out.println("objArray2 的数组元素："+objArray2);
      System.out.println("objArray 是否包含字符串common2? ： "
      +objArray.contains("common1"));
      System.out.println("objArray2 是否包含数组 objArray? ："
      +objArray2.contains(objArray) );
   }
}

结果：

objArray 的数组元素：[common1, common2]
objArray2 的数组元素：[common1, common2, notcommon, notcommon1]
objArray 是否包含字符串common2? ： true
objArray2 是否包含数组 objArray? ：false
判断数组是否相等
import java.util.Arrays;

public class Main {
   public static void main(String[] args) throws Exception {
      int[] ary = {1,2,3,4,5,6};
      int[] ary1 = {1,2,3,4,5,6};
      int[] ary2 = {1,2,3,4};
      System.out.println("数组 ary 是否与数组 ary1相等? ："
      +Arrays.equals(ary, ary1));
      System.out.println("数组 ary 是否与数组 ary2相等? ："
      +Arrays.equals(ary, ary2));
   }
}

结果：

数组 ary 是否与数组 ary1相等? ：true
数组 ary 是否与数组 ary2相等? ：false
数组并集
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;


public class Main {
    public static void main(String[] args) throws Exception {
        String[] arr1 = { "1", "2", "3" };
        String[] arr2 = { "4", "5", "6" };
        String[] result_union = union(arr1, arr2);
        System.out.println("并集的结果如下：");

        for (String str : result_union) {
            System.out.println(str);
        }
    }

    // 求两个字符串数组的并集，利用set的元素唯一性
    public static String[] union(String[] arr1, String[] arr2) {
        Set<String> set = new HashSet<String>();

        for (String str : arr1) {
            set.add(str);
        }

        for (String str : arr2) {
            set.add(str);
        }

        String[] result = {  };

        return set.toArray(result);
    }
}

结果：

并集的结果如下：
1
2
3
4
5
6
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