JAVA 基础入门课本例题代码(第二章)

Example01

public class Example01 {public static void main (String[] ags){int num=4;byte b=(byte)num;System.out.println(b);}}

Example02

public class Example02 {public static void main (String[] ags){byte a;int b=298;a=(byte)b;System.out.println("a="+a);System.out.println("b="+b);}}

Example03

public class Example03 {public static void main (String[] ags){byte a=1;byte b=2;byte c=(byte)(a+b);System.out.println("c="+c);}}

Example04

public class Example04 {public static void main (String[] ags){int a=12;{int b=13;System.out.println("a="+a);System.out.println("b="+b);}//b=a;System.out.println("a="+a);//System.out.println("b="+b);}}

Example05

public class Example05 {public static void main (String[] ags){short s=1;int a=10;s+=a;System.out.println("s="+s);}}

Example06

public class Example06 {public static void main (String[] ags){int a,b,c;a=b=c=0;boolean x,y;x=a>0&b++>1;System.out.println(x);System.out.println("b="+b);y=a>0&&c++>1;System.out.println(y);System.out.println("c="+c);}}

Example07

public class Example07 {public static void main (String[] ags){int x=5;if(x<10){x++;}System.out.println("x="+x);}}

Example08

public class Example08 {public static void main (String[] ags){int num=19;if(num%2==0){System.out.println("这是一个偶数");        }else{System.out.println("这是一个奇数");}}}

Example09

public class Example09 {public static void main (String[] ags){int great=75;if(great>80){System.out.println("该成绩的登级为优等");  }else if(great>70){System.out.println("该成绩的登级为良"); }else if (great>60){System.out.println("该成绩的登级为中");    }else{System.out.println("该成绩的登级为差"); }}}

Example10

public class Example10 {public static void main (String[] ags){int week=5;switch (week){case 1:System.out.println("星期一");break;case 2:System.out.println("星期二");break;case 3:System.out.println("星期三");break;case 4:System.out.println("星期四");break;case 5:System.out.println("星期五");break;case 6:System.out.println("星期六");break;case 7:System.out.println("星期天");break;default:System.out.println("输入的数字不正确.....");}}}

Example11

public class Example11 {public static void main (String[] ags){int week=2;switch (week){case 1:case 2:case 3:case 4:case 5:System.out.println("今天是工作日");break;case 6:case 7:System.out.println("今天是休息日");break;default:System.out.println("输入的数字不正确.....");}}}

Example12

public class Example12 {public static void main (String[] ags){int x=1;while (x<=4){System.out.println("x="+x);x++;}}}

Example13

public class Example13 {public static void main (String[] ags){int x=1;do{System.out.println("x="+x);x++;}while (x<=4);}}

Example14

public class Example14 {public static void main (String[] ags){int sum=0;for(int i=1;i<=4;i++){sum+=i;}System.out.println("sum="+sum);}}

Example15

public class Example15 {public static void main (String[] ags){int i,j;for(i=1;i<=9;i++){for(j=1;j<=i;j++){System.out.print("*");}System.out.print("\n");}}
}

Example16

public class Example16 {public static void main (String[] ags){int x=1;while (x<=4){System.out.println("x="+x);if(x==3){break;}x++;}}}

Example17

public class Example17 {public static void main (String[] ags){int i,j;itcast:for(i=0;i<9;i++){for(j=0;j<i;j++){if(i==3)break itcast;System.out.print("*");}System.out.print("\n");}}}

Example18

public class Example18 {public static void main (String[] ags){int sum=0;int i;for(i=1;i<=100;i++){if(i%2==0)continue;sum+=i;}System.out.println("sum="+sum);}}

Example19

public class Example19 {public static void main (String[] ags){for(int i=0;i<3;i++){for(int j=0;j<5;j++){System.out.print("*");}System.out.print("\n");}System.out.print("\n");for(int i=0;i<2;i++){for(int j=0;j<4;j++){System.out.print("*");}System.out.print("\n");}System.out.print("\n");for(int i=0;i<6;i++){for(int j=0;j<10;j++){System.out.print("*");}System.out.print("\n");}System.out.print("\n");}}

Example20

public class Example20 {public static void main (String[] ags){printRectaing(3,5);printRectaing(2,4);printRectaing(6,10);}public static void printRectaing(int height,int width){for(int i=0;i<height;i++){for(int j=0;j<width;j++){System.out.print("*"); }System.out.print("\n");} System.out.print("\n");}
}

Example21

public class Example21 {public static void main (String[] ags){int area=getAear(3,5);System.out.println("There area is "+area);}public static int getAear(int i,int j){return i*j;}}

Example22

public class Example22 {public static void main (String[] ags){int sum01=add01(1,2);int sum02=add02(1,2,3);double sum03=add03(1.2,2.3);System.out.println("sum01="+sum01);System.out.println("sum02="+sum02);System.out.println("sum03="+sum03);}public static int add01(int x,int y){return  x+y;}public static int add02(int x,int y,int z){return x+y+z;}public static double add03(double x,double y){return x+y;}
}

Example23

public class Example23 {public static void main (String[] ags){int sum01=add(1,2);int sum02=add(1,2,3);double sum03=add(1.2,2.3);System.out.println("sum01="+sum01);System.out.println("sum02="+sum02);System.out.println("sum03="+sum03);}public static int add(int x,int y){return x+y;}public static int add(int x,int y,int z){return x+y+z;}public static double add(double   x,double y){return x+y;}
}

Example24

public class Example24 {public static void main (String[] ags){int sum=getSum(4);System.out.println("sum="+sum);}public static int getSum(int n){if(n==1){return 1;}else {int temp=getSum(n-1);return temp+n;}}
}

Example25

public class Example25 {public static void main (String[] ags){int[]arr;arr=new int[4];System.out.println("arr[0]="+arr[0]);System.out.println("arr[1]="+arr[1]);System.out.println("arr[2]="+arr[2]);System.out.println("arr[3]="+arr[3]);}}

Example26

public class Example26 {public static void main (String[] ags){int []arr= new int [4];arr[0]=1;arr[1]=2;System.out.println("arr[0]="+arr[0]);System.out.println("arr[1]="+arr[1]);System.out.println("arr[2]="+arr[2]);System.out.println("arr[3]="+arr[3]);}}

Example27

public class Example27 {public static void main (String[] ags){int[]arr={1,2,3,4};System.out.println("arr[0]="+arr[0]);System.out.println("arr[1]="+arr[1]);System.out.println("arr[2]="+arr[2]);System.out.println("arr[3]="+arr[3]);}}

Example28

public class Example28 {public static void main (String[] ags){int []arr=new int [4];System.out.println("arr[3]="+arr[3]);//System.out.println("a[4]="+a[4]);}}
/**这部分代码是为了验证数组的角标是从0开始的，四个数组元素即是arr[0]到arr[3]*/

Example29

public class Example29 {public static void main (String[] ags){int []arr=new int [2];System.out.println("arr[0]="+arr[0]);System.out.println("arr[1]="+arr[1]);arr=null;System.out.println("arr[0]="+arr[0]);System.out.println("arr[1]="+arr[1]);}}

Example30

public class Example30 {public static void main (String[] ags){int[]arr={1,2,3,4};for(int i=0;i<arr.length;i++){System.out.println(arr[i]);}}}

Example31

public class Example31 {public static void main (String[] ags){int []arr={8,4,3,5,7,3};int max=getMax(arr);System.out.println(max);}static int getMax(int []arr){int max=arr[0];for(int i=1;i<arr.length;i++){if(max<arr[i])max=arr[i];}return max;}
}

Example32

public class Example32 {public static void main (String[] ags){int []arr={9,8,3,5,2};System.out.print("冒泡排序前：");printArray(arr);bubbleSort(arr);System.out.println("冒泡排序后：");printArray(arr);}public static void printArray (int []arr){for(int i=0;i<arr.length;i++){System.out.print(arr[i]+" ");//数字后面加一个空格}System.out.print("\n");}public static void bubbleSort (int []arr){for(int i=0;i<arr.length-1;i++){for(int j=0;j<arr.length-i-1;j++){if(arr[i]>arr[i+1]){int temp=arr[j];arr[j]=arr[j+1];arr[j+1]=temp;}}System.out.printf("第"+(i+1)+"轮排序后：");printArray(arr);}}
}

Example33

public class Example33 {public static void main (String[] ags){int [][]arr=new int [3][];arr[0]=new int []{11,12};arr[1]=new int []{21,22,23};arr[2]=new int []{31,32,33,34};int sum=0;for(int i=0;i<arr.length;i++){int groupSum=0;for(int j=0;j<arr[i].length;j++){groupSum=groupSum+arr[i][j];}sum+=groupSum;System.out.println("第"+(i+1)+"小组销售额为："+groupSum+"万元");}System.out.println("总销售额为："+sum+"万元");}}

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JAVA 基础入门课本例题代码(第二章)

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