分别用for. while 和do-while循环语句以及递归方法计算n，并输出算式。用java

使用for循环:

public static int calculateWithForLoop(int n) {
    int result = 0;
    String formula = "";
    for (int i = 1; i <= n; i++) {
        result += i;
        if (i == 1) {
            formula += i;
        } else {
            formula += "+" + i;
        }
    }
    System.out.println(formula + "=" + result);
    return result;
}

使用while循环:

public static int calculateWithWhileLoop(int n) {
    int result = 0;
    String formula = "";
    int i = 1;
    while (i <= n) {
        result += i;
        if (i == 1) {
            formula += i;
        } else {
            formula += "+" + i;
        }
        i++;
    }
    System.out.println(formula + "=" + result);
    return result;
}

使用do-while循环:

public static int calculateWithDoWhileLoop(int n) {
    int result = 0;
    String formula = "";
    int i = 1;
    do {
        result += i;
        if (i == 1) {
            formula += i;
        } else {
            formula += "+" + i;
        }
        i++;
    } while (i <= n);
    System.out.println(formula + "=" + result);
    return result;
}

使用递归方法:

public static int calculateWithRecursion(int n) {
    if (n == 1) {
        System.out.println("1=1");
        return 1;
    } else {
        int result = n + calculateWithRecursion(n - 1);
        System.out.println(getFormula(n) + "=" + result);
        return result;
    }
}

public static String getFormula(int n) {
    if (n == 1) {
        return "1";
    } else {
        return getFormula(n - 1) + "+" + n;
    }
}

以上代码中，每个方法都用一个循环语句或递归方法计算1到n的和，并输出相应的算式。