Java学习笔记（19）

数组使用

普通的For循环

public static void main(String[] args) {
    int[] arrays = {1,2,3,4,5};
    //打印数组所有元素
    for (int i = 0; i < arrays.length; i++) {
        System.out.println(arrays[i]);
    }
    System.out.println("===============");
    //计算所有元素的和
    int sum = 0;
    for (int i = 0; i < arrays.length; i++) {
        sum += arrays[i];
    }
    System.out.println("sum = "+ sum);
    System.out.println("===============");
    //查找最大元素
    int max = arrays[0];
    for (int i = 1; i < arrays.length; i++) {
        if(arrays[i] > max){
            max = arrays[i];
        }
    }
    System.out.println("max = "+ max);
}

For-Each 循环

public static void main(String[] args) {
    int[] arrays = {1,2,3,4,5};
    //JDK 1.5,没有下标   
    for (int array : arrays) {
        System.out.println(array);
    }
}

数组作方法入参

public static void main(String[] args) {
    int[] arrays = {1,2,3,4,5};
    printArray(arrays);
}
//打印数组元素
public static void printArray(int[] arr){
    for (int i = 0; i < arr.length; i++) {
        System.out.print(arr[i] + " ");
    }
}

数组作返回值

public static void main(String[] args) {
    int[] arrays = {1,2,3,4,5};
    int[] reserve = reverse(arrays);
    printArray(reserve);
}
//打印数组元素
public static void printArray(int[] arr){
    for (int i = 0; i < arr.length; i++) {
        System.out.print(arr[i] + " ");
    }
}
//反转数组
public static int[] reverse(int[] arr){
    int[] result = new int[arr.length];
    //反转操作
    for (int i = 0,j = result.length - 1; i < arr.length; i++,j--) {
        result[j] = arr[i];
    }
    return result;
}