您当前的位置： 首页 > 学无止境 > 心得笔记 网站首页心得笔记

【第4章：数组与方法】_数组的定义及使用

发布时间：2020-11-18 16:29:24编辑：雪饮阅读（）

 数组的定义

public class Hello{
       public static void main(String args[]){
              int score[]=null;
              //为当前定义数组开辟3个空间
              score=new int[3];
              System.out.println(score[0]);
              System.out.println(score[1]);
              System.out.println(score[2]);
       }
}
默认情况下数组没有被填充每个元素时这里由于是int型数组，所以每个元素的值默认为0

int score[]=null;也可以直接简写为int score[];
public class Hello{
       public static void main(String args[]){
              int score[];
              score=new int[3];
              System.out.println(score[0]);
              System.out.println(score[1]);
              System.out.println(score[2]);
       }
}

数组长度可以用该数组变量的length获取
public class Hello{
       public static void main(String args[]){
              int score[];
              score=new int[3];
              System.out.println(score.length);
       }
}

数组的填充（初始化）
用数组指定下标进行填充数组叫做数组的动态初始化
public class Hello{
       public static void main(String args[]){
              int score[];
              score=new int[3];
              for(int x=0;x<score.length;x++){
                     score[x]=x+1;
              }
              for(int x=0;x<score.length;x++){
                     System.out.println(score[x]);
              }
       }
}

数组的静态初始化
上面的初始化方式是指定下标进行初始化的，也可以定义时候直接一起定义，这样连开辟空间都不用了，这种叫做静态初始化。
public class Hello{
       public static void main(String args[]){
              int score[]={91,92,94,95,97};
              for(int x=0;x<score.length;x++){
                     System.out.println(score[x]);
              }
       }
}

数组求最值
public class Hello{
       public static void main(String args[]){
              int score[]={91,92,94,95,97,33,1,5,9};
              int max=0;
              int min=0;
              max=min=score[0];
              for(int x=0;x<score.length;x++){
                     if(score[x]>max){
                            max=score[x];
                     }
                     if(score[x]<min){
                            min=score[x];
                     }
              }
              System.out.println(max);
              System.out.println(min);
       }
}

排序
public class Hello{
       public static void main(String args[]){
              int score[]={4,1,2,7,5,8,3,9,21,15,25,19};
              for(int i=1;i<score.length;i++){
                     for(int j=0;j<score.length;j++){
                            if(score[i]<score[j]){
                                   int temp=score[i];
                                   score[i]=score[j];
                                   score[j]=temp;
                            }
                     }
                     System.out.print("第"+i+"次排序的结果:\t");
                     for(int j=0;j<score.length;j++){
                            System.out.print(score[j]+"\t");
                     }
                     System.out.println("");
              }
              for(int i=0;i<score.length;i++){
                     System.out.print(score[i]+"\t");
              }
       }
}

二维数组
public class Hello{
       public static void main(String args[]){
              int score[][]=new int[4][3];
              score[0][1]=30;
              score[1][0]=31;
              score[2][2]=32;
              score[3][1]=33;
              score[1][1]=30;
              for(int i=0;i<score.length;i++){
                     System.out.println(i);
                     for(int j=0;j<score[i].length;j++){
                            System.out.println("\t"+score[i][j]);
                     }
                    
              }
       }
}
开辟第一维4个空间，第一维的每个二维开辟3个空间。

静态二维数组
public class Hello{
       public static void main(String args[]){
              int score[][]={
                     {67,61},{78,89,83},{99,100,98,66,65}
              };
              for(int i=0;i<score.length;i++){
                     System.out.println(i);
                     for(int j=0;j<score[i].length;j++){
                            System.out.println("\t"+score[i][j]);
                     }
                    
              }
       }
}

三维数组
public class Hello{
       public static void main(String args[]){
              int score[][][]={
                     {
                            {67,61},{78,89,83},{99,100,98,66,65}
                     },
                     {
                            {63,60},{71,19,23},{9,10,108,6,75}
                     }
                    
              };
              for(int i=0;i<score.length;i++){
                     System.out.println(i);
                     for(int j=0;j<score[i].length;j++){
                            System.out.println("\t"+i+"_"+j);
                            for(int z=0;z<score[i][j].length;z++){
                                   System.out.println("\t\t"+score[i][j][z]);
                            }
                     }
                    
              }
       }
}