Struct
顺序
package com.zzl.struct;
public class ShunXuDemo1 {
public static void main(String[] args) {
System.out.println("hello1");
System.out.println("hello2");
System.out.println("hello3");
System.out.println("hello4");
System.out.println("hello5");
}
}
Switch
package com.zzl.struct;
public class SwitchDemo1 {
public static void main(String[] args) {
//(没有break)case 穿透 switch 匹配一个值
char grade = 'b';
switch (grade){
case 'a':
System.out.println("优秀");
break;//可选
case 'b':
System.out.println("良好");
break;
case 'c':
System.out.println("及格");
break;
case 'd':
System.out.println("再接再厉");
break;
case 'e':
System.out.println("挂科");
break;
default:
System.out.println("未知等级");
}
}
}
String
package com.zzl.struct;
public class SwitchDemo2 {
public static void main(String[] args) {
String name = "狂神";
//字符的本质还是数字
//反编译
switch (name){
case "周子龙":
System.out.println("周子龙");
break;
case "小个":
System.out.println("小个");
break;
case "狂神":
System.out.println("狂神");
break;
default:
System.out.println("弄啥来");
}
}
}
if
判断字符串是否相等//equals
package com.zzl.struct;
import java.util.Scanner;
public class IfDemo1 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("请输入一个内容:");
String s = scanner.nextLine();
//equals:判断字符串是否相等
if(s.equals("Hello")) {
System.out.println(s);
}
System.out.println("end");
scanner.close();
}
}
if else
package com.zzl.struct;
import java.util.Scanner;
public class IfDemo1 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("请输入一个内容:");
String s = scanner.nextLine();
//equals:判断字符串是否相等
if(s.equals("Hello")) {
System.out.println(s);
}
System.out.println("end");
scanner.close();
}
}
if else if
package com.zzl.struct;
import java.util.Scanner;
public class ifDemo3 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
/*
if语句至多有一个else语句,else语句在所有的else if语句之后
if语句可以有若干个else if语句,他们必须在else语句之前
一旦其中一个else if语句检测为true 其他的else if以及else语句都将跳过执行
*/
int i = scanner.nextInt();
if(i == 100){
System.out.println("满分");
} else if (i<100 && i>=90) {
System.out.println("A");
} else if (i<90 && i>=60) {
System.out.println("B");
}else if (i<60 && i>=0){
System.out.println("不及格");
}else {
System.out.println("不合法");
}
scanner.close();
}
}
循环结构体
while
package com.zzl.struct;
public class WhileDemo1 {
public static void main(String[] args) {
int i = 0;
while(i<100){
i++;
System.out.println(i);
}
}
}
package com.zzl.struct;
public class WhileDemo2 {
public static void main(String[] args) {
while (true){
//等待客户端链接
//定时检查
//。。。。
}
}
}
package com.zzl.struct;
public class WhileDeom3 {
public static void main(String[] args) {
int i = 0;
int sum = 0;
while (i<100){
i++;
sum +=i;
}
System.out.println(sum);
}
}
do while
package com.zzl.struct;
public class DoWhileDemo1 {
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.zzl.struct;
public class DoWhileDemo2 {
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);
System.out.println(a);
}
}
至少执行一次
for
package com.zzl.struct;
public class ForDemo1 {
public static void main(String[] args) {
int a = 1;//初始条件
while(a<=100){ //条件判断
System.out.println(a); //循环体
a +=1; //迭代
}
System.out.println("while循环结束!");
//初始化//条件判断//迭代 for循环语句是支持迭代的一种通用结构,是最有效,最灵活的循环结构。
for (int i = 1; i<=100;i++){
System.out.println(i);
}
/*
*/
System.out.println("for循环结束");
}
}
方法
方法的重载
package com.zzl.mathod;
public class Demo1 {
//main方法
public static void main(String[] args) {
//实际参数:实际调用传递给他的参数
int sum = add(1,2);
int sum2 = add(1,2,3);
System.out.println(sum);
System.out.println(sum2);
}
//加法
//形式参数:用来定义的作用
public static int add(int a,int b){
return (a+b);//非void一定要有return
}
public static int add(int a,int b,int c){
return (a+b+c);
}
}
//方法重载
//方法名必须相同
//参数列表必须不同(个数不同,或类型不同,参数排列顺序不同等)。
//方法的返回类型可以相同也可以不同。
//仅仅返回类型不同不足以成为方法的重载
数组
数组初始化,赋值
package com.zzl.arry;
public class Demo2 {
public static void main(String[] args) {
//静态初始化:创建+赋值
int[] a = {1,2,3,4,5,6,7};
System.out.println(a[0]);
//动态初始化
int[] b = new int[10];
b[0] = 10;
System.out.println(b[0]);//处在隐式初始化如b[1] = 0;
}
}
//数组一旦被创建,他的大小就是不可以改变的
//元素类型必须相同
//数组对像本身是在堆中的
数组的使用
package com.zzl.arry;
import com.sun.org.apache.bcel.internal.generic.ARETURN;
public class Demo4 {
public static void main(String[] args) {
int[] arrays ={1,2,3,4,5};
//JDK1.5,没有下标
//for (int array : arrays) {
// System.out.println(array);
int[] result = reverse(arrays);
print(result);
}
//反转数组
public static int[] reverse(int [] arrays){
int[] result = new int[arrays.length];
for (int i = 0,j= arrays.length-1; i < arrays.length; i++,j--) {
result[j] = arrays[i];
}
return result;
}
//打印数组元素
public static void print(int[] arrays){
for (int i = 0; i < arrays.length; i++) {
System.out.println(arrays[i]+" ");
}
}
}
二维数组
package com.zzl.arry;
public class Demo5 {
public static void main(String[] args) {
//[4][2]
int[][] array = {{1,2},{3,4},{5,6},{7,8}};
for (int i = 0; i < array.length; i++) {
for (int i1 = 0; i1 < array[i].length; i1++) {
System.out.println(array[i][i1]);
}
}
}
public static void print(int[] arrays){
for (int i = 0; i < arrays.length; i++) {
System.out.println(arrays[i]+" ");
}
}
}
冒泡排序
package com.zzl.arry;
import java.util.Arrays;
public class Demo7 {
public static void main(String[] args) {
int[] a = {123,43,53,55,8};
int[] maopao = maopao(a);
System.out.println(Arrays.toString(maopao));
}
//冒泡排序
//1.比较数组中相邻的元素
//2.每一次比较都会产生一个最大或者最小的数字
//3.下一轮会减少一次循环
//int[] a = {123,43,53,646,8};
public static int[] maopao(int[] a){
int t = 0;
//外层循环,判断我们这个要走几次
for (int i = 0; i < a.length-1; i++) {
//内层循环比较两个数,如果第一个数大就与第二个数交换位置
for (int i1 = 0; i1 < a.length-1-i; i1++) {
if (a[i1+1]>a[i1]){
t = a[i1];
a[i1] = a[i1+1];
a[i1+1] = t;
}
}
}
return a;
}
}
Array
package com.zzl.arry;
import java.util.Arrays;
public class Demo6 {
public static void main(String[] args) {
int[] a = {1,32323,34,54,65,5757,8};
//System.out.println(a);//[I@7f31245a
//打印数组
//System.out.println(Arrays.toString(a));
//print(a);
//Arrays.sort(a);//排序
//System.out.println(Arrays.toString(a));
Arrays.fill(a,1);//填充
System.out.println(Arrays.toString(a));
}
public static void print(int a[]){
for (int i = 0; i < a.length; i++) {
System.out.print(a[i]+",");
}
}
}
标签:Java,进阶,int,System,static,println,public,out
From: https://www.cnblogs.com/zzl990110/p/17971265