for-each循环的认识、定义、适用对象、举例、局限性

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for(元素类型T 每次循环元素的名称 : 循环对象){
　　　　//对定义的名称进行操作
　}

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	public static void main(String[] args) {
String[] demo = {"a", "b", "c"};
for (String t :demo ) {
System.out.println(t);
}
}

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public static void main(String[] args) {
List<String> list = new ArrayList();
list.add("a");
list.add("b");
list.add("c");
for(String str : list){
System.out.println(str);
}
}

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import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class test{
public static void main(String[] args) {
String[] names = {"ming", "fei"};
for (String name : names) {
name = "xin";
}
//foreach
System.out.println("foreach:"+Arrays.toString(names));
//for
for (int i = 0; i < names.length; i++) {
names[i] = "xin";
}
System.out.println("for:"+Arrays.toString(names));
}
}

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import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class test {
public static void main(String[] args) {
List<String> names = new ArrayList<String>();
names.add("ming");
names.add("fei");
//foreach
for(String name:names){
name = "uzi";
}
System.out.println(Arrays.toString(names.toArray()));
//for
for (int i = 0; i < names.size(); i++) {
names.set(i,"uzi");
}
System.out.println(Arrays.toString(names.toArray()));
}
}

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import java.io.File;
public class Demo {
public static void main(String[] args){
File file=new File("D:/apache-maven1");
String[] files=file.list();
for(int i=0;i<files.length;i++){
System.out.println(files[i]);
}
System.out.println(files.length);
}
}

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import java.net.InetAddress;
import java.net.UnknownHostException;
public class Demo {
public static void main(String[] args) throws UnknownHostException {
InetAddress host = InetAddress.getLocalHost();
String ip =host.getHostAddress();
System.out.println("本机ip地址：" + ip);
}
}

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import java.util.Random;
public class Demo {
static char[] chars = {'0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f','g','h',
'i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
public static String getStr(int i){
StringBuffer string =
new StringBuffer();
Random random = new Random();
while(i-->0){
//获取随机生成的下标
int x = random.nextInt(chars.length);
string.append(chars[x]);
}
return string.toString();
}
public static void main(String[] args) throws Exception {
int i=6;
String string = getStr(i);
System.out.println(string);
}
}