while迴圈

package struct;

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

}

for迴圈

package struct;

public class ForDemo01 {
    //練習1：計算0到100之間的奇數和偶數的和
    public static void main(String[] args) {
        int oddSum = 0;
        int evenSum = 0;

        for (int i = 0; i <=100; i++) {
            //與while那邊進行對比
            if (i % 2 == 0) {
                evenSum += i;
            } 
 
else {
                oddSum += i;
            }
        }
        System.out.println("奇數的和"+oddSum);
        System.out.println("偶數的和"+evenSum);


    }
}

for迴圈執行一次迴圈後更新

package struct;

public class forDemo02 {
public static void main(String[]args){
    for(int j=1;j<=9;j++){
        System.out.println(
 
"");
        for(int i=1;i<=j;i++) {
            System.out.print(j+"*"+i+"="+j*i+" ");
        }
    }
}
}

九九迴圈表

增強for迴圈

break和continue

Test

1.輸出三角形

package struct;

public class TestDemo01 {
    //列印三角形 5行
    public static void main(String[]args){
    for(int i=1;i<=5;i++) {
        System.out.println("");
        for(int j=5;j>i;j--){
            System.out.print(" ");
        }
        for(int j=1;j<=i;j++){
            System.out.print("*");
        }
        for(int j=1;j<i;j++){
            System.out.print("*");
        }


    }
    }
}