Java的递归求1到100求和！

版权声明：本文为博主原创文章，转载请注明出处。 https://blog.csdn.net/yuankundong/article/details/53069287

public class SumDemo {
    //1到100相加
    public static void main(String[] args) {
        System.out.println("方法1："+sum1());
        System.out.println("方法2："+sum2());
        System.out.println("方法3："+sum3(100));
}

<span class="hljs-comment">//方法1 while循环</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span> <span class="hljs-title">sum1</span>(){
    <span class="hljs-keyword">int</span> sum = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">int</span> i = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">while</span>(i&lt;=<span class="hljs-number">100</span>){          
        sum+=i;
        i++;
    }

    <span class="hljs-keyword">return</span> sum;

}

<span class="hljs-comment">//方法2 for循环</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span> <span class="hljs-title">sum2</span>(){
    <span class="hljs-keyword">int</span> sum = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">for</span>(<span class="hljs-keyword">int</span> i=<span class="hljs-number">0</span>;i&lt;=<span class="hljs-number">100</span>;i++){
        sum+=i;
    }

    <span class="hljs-keyword">return</span> sum;

}
<span class="hljs-comment">//方法3 递归</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span> <span class="hljs-title">sum3</span>(<span class="hljs-keyword">int</span> num){
    <span class="hljs-keyword">if</span>(num==<span class="hljs-number">1</span>){
        <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>;
    }
    <span class="hljs-keyword">else</span>{
        <span class="hljs-keyword">return</span> num+sum3(num-<span class="hljs-number">1</span>);
    }
}

}

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输出结果：

方法1：5050
方法2：5050
方法3：5050
  
  

   
   
1
   
   
2
   
   
3
  
  

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            </div>

版权声明：本文为博主原创文章，转载请注明出处。 https://blog.csdn.net/yuankundong/article/details/53069287

public class SumDemo {
    //1到100相加
    public static void main(String[] args) {
        System.out.println("方法1："+sum1());
        System.out.println("方法2："+sum2());
        System.out.println("方法3："+sum3(100));
}

<span class="hljs-comment">//方法1 while循环</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span> <span class="hljs-title">sum1</span>(){
    <span class="hljs-keyword">int</span> sum = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">int</span> i = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">while</span>(i&lt;=<span class="hljs-number">100</span>){          
        sum+=i;
        i++;
    }

    <span class="hljs-keyword">return</span> sum;

}

<span class="hljs-comment">//方法2 for循环</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span> <span class="hljs-title">sum2</span>(){
    <span class="hljs-keyword">int</span> sum = <span class="hljs-number">0</span>;
    <span class="hljs-keyword">for</span>(<span class="hljs-keyword">int</span> i=<span class="hljs-number">0</span>;i&lt;=<span class="hljs-number">100</span>;i++){
        sum+=i;
    }

    <span class="hljs-keyword">return</span> sum;

}
<span class="hljs-comment">//方法3 递归</span>
<span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">int</span> <span class="hljs-title">sum3</span>(<span class="hljs-keyword">int</span> num){
    <span class="hljs-keyword">if</span>(num==<span class="hljs-number">1</span>){
        <span class="hljs-keyword">return</span> <span class="hljs-number">1</span>;
    }
    <span class="hljs-keyword">else</span>{
        <span class="hljs-keyword">return</span> num+sum3(num-<span class="hljs-number">1</span>);
    }
}