Java循环结构

循环结构

• while 循环
  

  package com.sxl.struct;
  
  public class WhileDemo01 {
      public static void main(String[] args) {
          int i = 0;
          while (i < 100){
              i++;
              System.out.println(i);
          }
      }
  }
  
  
  package com.sxl.struct;
  
  public class WhileDemo02 {
      public static void main(String[] args) {
          int i = 0;
          int sum = 0;
          while (i <= 100){
              sum = sum + i;
              i++;
          }
          System.out.println(sum);
      }
  }
  
  

• do...while 循环

package com.sxl.struct;

public class DoWhileDemo01 {
    public static void main(String[] args) {
        int i = 0;
        int sum = 0;
        do {
            sum = sum + i;
            i++;
        }while (i<=100);
        System.out.println(sum);
    }
}

package com.sxl.struct;

public class DoWhileDemo02 {
    public static void main(String[] args) {
        int a = 0;
        while (a < 0){
            System.out.println(a);
            a++;
        }
        System.out.println("===============");
        do {
            System.out.println(a);
            a++;
        }while (a<0);
    }
}

• for循环
  

  package com.sxl.struct;
  
  public class ForDemo01 {
      public static void main(String[] args) {
          //输出1到100的奇数和以及偶数和
          int oddSum = 0;
          int evenSum = 0;
          for (int i = 0; i <= 100; i++) {
              if (i%2 != 0){
                  oddSum += i;
              }else{
                  evenSum += i;
              }
          }
          System.out.println("1到100的奇数和为：" +oddSum);
          System.out.println("1到100的偶数和为：" +evenSum);
      }
  }
  
  
  
  package com.sxl.struct;
  
  public class ForDemo02 {
      public static void main(String[] args) {
          //输出1到1000能被5整除到数，并且每行输出3个数
          for (int i = 1; i <= 1000; i++) {
              if (i%5 == 0){
                  System.out.print(i+"\t");
              }
              if (i%(5*3) == 0){
                  System.out.println();
              }
          }
      }
  }
  
  
  package com.sxl.struct;
  
  public class ForDemo03 {
      //打印九九乘法表
      //1.先打印第一列
      //2、我们用固定到1在用一个循环抱起来
      //3、去掉重复项   i<=j
      //4、样式调整
      public static void main(String[] args) {
          for (int j = 1; j <= 9; j++) {
              for (int i = 1; i <= j; i++) {
                  System.out.print(i+"*"+j +"=" + j*i +"\t");
              }
              System.out.println();
          }
      }
  }
  
  

• 在java5中引入了一种主要用于数组的增强型 for 循环
  

  package com.sxl.struct;
  
  public class ForDemo04 {
      public static void main(String[] args) {
          int[] arry = {10, 20, 30, 40};
          for (int i = 0; i < 4; i++){
              System.out.println(arry[i]);
          }
          System.out.println("===================");
          //增强for循环
          for (int x:arry){
              System.out.println(x);
          }
      }
  }