System类中的arraycopy，StringBuilder的append、toString方法，包装类，基本数据类型和字符串之间的转换

import java.util.Arrays;
import java.util.Scanner;

public class StringBuilderDemo {
    public static void main(String[] args) {
        int[] src = {1,2,3,4,5,6};
        int[] dest = {4,5,6,7,8,9};
        System.arraycopy(src,1,dest,0,3);
        for (int i : dest
             ) {
            System.out.println(i);
        }
        System.out.println(Arrays.toString(dest));
        System.out.println("---------------");

        Scanner scanner = new Scanner(System.in);
        int nextInt = scanner.nextInt();
        String next = scanner.next();

        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append(next).append(nextInt).append('好').append(true).append(545.45564);
        System.out.println(stringBuilder);
        String s = stringBuilder.toString();
        System.out.println(s);
    }
}

public class XiangDemo {
    public static void main(String[] args) {
        int int1 = 100;
        Integer Int1 = 100;

        //基本类型->字符串
        String s = int1 + "";
        System.out.println(s+200);
        String s1 = Int1.toString();
        System.out.println(s1+200);
        String s2 = String.valueOf(132);
        System.out.println(s2+2121);

        //字符串->基本类型
        int i = Integer.parseInt(s);
        System.out.println(i+200);
    }
}