[Java] 常用类-01 String / StringBuffer

package com.bjsxt.chap6;
/**
 * @author hp
 *
 */
public class Test {
    public static void main(String[] args) {
        String s1 = "hello";
        String s2 = "world!";
        String s3 = "hello";
        System.out.println(s1 == s3);
        
        s1 = new String("hello");
        s2 = new String("hello");
        System.out.println(s1 == s3);
        System.out.println(s1.equals(s3));
        
        char c[] = {'s', 'u', 'n', ' ', 'j', 'a', 'v', 'a'};
        String s4 = new String(c);
        String s5 = new String(c, 4, 3); // 数组， 下标， 长度
        System.out.println(s4 + '\n' + s5);
        
        System.out.println(s4.charAt(1));
        System.out.println(s4.length());
        System.out.println(s4.indexOf("java"));
        
        System.out.println(s4.replaceAll("sun", "oracle"));
    }
}

package com.bjsxt.chap6;

public class TestStringCase {
    public static void main(String[] args) {
        String s = "ABAabb$&^$#BAAb898B#@%aa";
        int cU = 0, cL = 0, cO = 0;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);

            if (c >= 'A' && c <= 'Z') {
                cU++;
            } else if (c >= 'a' && c <= 'z') {
                cL++;
            } else {
                cO++;
            }
        }

        System.out.println("小写：" + cL);
        System.out.println("大写：" + cU);
        System.out.println("其他：" + cO);
        
        int lCount = 0, uCount = 0, oCount = 0;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (Character.isLowerCase(c)) {
                lCount++;
            } else if (Character.isUpperCase(c)) {
                uCount++;
            } else {
                oCount++;
            }
        }
        
        System.out.println("小写：" + lCount);
        System.out.println("大写：" + uCount);
        System.out.println("其他：" + oCount);
        
        String ss = "sunjavahpjavaokjavajjavahahajavajavagoodjava";
        
        String sToFind = "java";
        int count = 0;
        int index = -1;
        
        while((index = ss.indexOf(sToFind)) != -1) {
            ss = ss.substring(index + sToFind.length());
            count ++;
        }
        
        System.out.println(count);
    }
}

package com.bjsxt.chap6;

public class TestBuffer {
    public static void main(String[] args) {
        String s = "Mircosoft";
        char arr[] = {'a', 'b', 'c'};
        StringBuffer sb1 = new StringBuffer(s);
        sb1.append('/').append("IBM");
        System.out.println(sb1);
        StringBuffer sb2 = new StringBuffer("数字");
        for (int i = 0; i <= 9; i++) {
            sb2.append(i);
        }
        System.out.println(sb2);
        
        sb2.delete(8, 11).insert(0, arr);
        
        System.out.println(sb2);
        System.out.println(sb2.reverse());
    }
}

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