Java main函数的命令行参数

main函数里面的String args[]的作用

可以用于从外部向代码传数据

public class Test{public static void main (String args[]){for(int i=0;i<args.length;i++){System.out.print(args[i]+" ");}}}

简单加法器

public class Test{public static void main (String args[]){if (args.length<3){System.out.println("Usage:java Test \"n1\" \"cp\" \"n2\"");System.exit(-1);}try{double d1 = Double.parseDouble(args[0]);double d2 = Double.parseDouble(args[2]);double d = 0;if (args[1].equals("+")){d=d1+d2;}else if (args[1].equals("x")){d=d1*d2;}else if (args[1].equals("-")){d=d1-d2;}else if (args[1].equals("/")){d=d1/d2;}else{System.out.println("Error operation!");System.exit(-1);}System.out.println(d);}catch (NumberFormatException e){System.out.println("你数字敲错了！");}}}

选择排序

public class NumSort{public static void main(String[] args){int[] a =new int[args.length];for (int i=0;i<args.length;i++){a[i] =Integer.parseInt(args[i]);}print(a);selectSort(a);print(a);}private static void selectSort(int[] a){int k,temp;for (int i=0;i<a.length;i++){k=i;for(int j=k+1;j<a.length;j++){if (a[j]<a[k]){k=j;}}if (k!=i){temp=a[i];a[i]=a[k];a[k]=temp;}}}private static void print(int[] a){for(int i=0;i<a.length;i++){System.out.print(a[i]+" ");}System.out.println();}}