方法一：indexOf(String s)

可以配合indexOf(String s)的使用，如果包含，返回的值是包含该子字符串在父类字符串中起始位置；如果不包含必定全部返回值为-1

public void test02() {
		String str1="张三";
		String str2="是一个张三大笨蛋";
		if(str2.indexOf(str1)!=-1) {
			System.out.println("存在包含关系");
		}else {
			System.out.println("不存在包含关系");
		}
	}

方法二：contains（）

String类型有一个方法：contains（）,该方法是判断字符串中是否有子字符串。如果有则返回true，如果没有则返回false。

package api.api;

public class App1 {

  public static void main(String[] args) {
    String num = "WKCON190400111";
    if (num.contains("CON")) {
      System.out.println(1);
    } else {undefined
      System.out.println(2);
    }
  }
}

输出结果：
1

String.indexOf与String.contains效率测试

String.indexOf与String.contains都是判断字符串是否包含另一个字符串的方法。String.indexOf存在返回第一个字符索引位置,不存才返回-1;String.contains存在返回true,不存在返回false。

现在测试两个方法的效率,不区分大小写判断。一个字符串判断是否含有48个单词中的单词,执行一百万次。

结论 : String.indexOf 效率更高。 (或许我的测试方法有误,欢迎指正)

先上结果,如下

1000000*48 次 String.contains 耗时:4691 ms
1000000*48 次 String.indexOf  耗时:31 ms
^str1:全部存在(小写)-------------------------------------------------------------------
 
1000000*48 次 String.contains 耗时:3735 ms
1000000*48 次 String.indexOf  耗时:17 ms
^str2:全部存在(大写)-------------------------------------------------------------------
 
1000000*48 次 String.contains 耗时:37 ms
1000000*48 次 String.indexOf  耗时:14 ms
^str3:部分存在------------------------------------------------------------------------
 
1000000*48 次 String.contains 耗时:17 ms
1000000*48 次 String.indexOf  耗时:14 ms
^str4:不存在(数字、字符、字母)----------------------------------------------------------
 
1000000*48 次 String.contains 耗时:16 ms
1000000*48 次 String.indexOf  耗时:16 ms
^str5:不存在(字母)--------------------------------------------------------------------
 
1000000*48 次 String.contains 耗时:17 ms
1000000*48 次 String.indexOf  耗时:14 ms
^str6:不存在(数字)--------------------------------------------------------------------
 
1000000*48 次 String.contains 耗时:17 ms
1000000*48 次 String.indexOf  耗时:14 ms
^str7:不存在(字符)--------------------------------------------------------------------

测试代码如下

public class StringContainsOrIndexOfVelocity {
 
    private static final String base = "article.add,article.update,article.delete,article.view," +
            "category.add,category.update,category.delete,category.view," +
            "user.add,user.update,user.delete,user.view," +
            "role.add,role.update,role.delete,role.view," +
            "news.add,news.update,news.delete,news.view," +
            "category.add,category.update,category.delete,category.view," +
            "Threading.add,Threading.update,Threading.delete,Threading.view," +
            "System.add,System.update,System.delete,System.view," +
            "Generic.add,Generic.update,Generic.delete,Generic.view," +
            "Collections.add,Collections.update,Collections.delete,Collections.view," +
            "Tasks.add,Tasks.update,Tasks.delete,Tasks.view," +
            "CslApp.add,CslApp.update,CslApp.delete,CslApp.view";
 
    private static final String[] bases = base.toUpperCase().split(",");
 
    private static final String str1 = base;
    private static final String str2 = base.toUpperCase();
    private static final String str3 = "ns.add,Collections.update,Collections.delete,Collections.ving.add,Threading.update,Threading.delete,Threading.add,role.update,role.delete,role.vietions.1";
    private static final String str4 = "klsjflsjdfoadsfi;jadls;fjoashgewnaiefahefoia274923472395674358920374uy3fh2f92yfh02ydsuhawe9f''''''//>>>>><<<~~~~!!@#$%^&&hrhfa8fewy7rt23984g23fhaiouf";
    private static final String str5 = "skdhlskdjfasd;faioegneohfaeofjaoeihfjaopihfeoasmgvlandihfawieughfyoiebfinlkjdsfoiajheiohioejfaesafkhjasdhflakdjsfasdfaldfadfsdjflsfjaldfjlajdflajldjflkaf";
    private static final String str6 = "239875824368517230941327041230740471674083295738473297589327492347239567435892037409827304203406324672937027394623764170324671324891748192374937489273489";
    private static final String str7 = "`--==-`-=-=-`=-`=-`==-@#$%^&*((*&^%$#$#$@#@##!@#$$%&^*()()())>><:;'''''''//>>>>><<<~~~~!!@#$%^&&*@#$%^&*()#$%^&*(*&^%$#@#$%^&*(*&^%$#@!@#$%^&*(*&^%$#";
 
    public static void main(String[] args) {
        int count = 1000000;
        test(str1, count);
        System.out.println("^str1:全部存在(小写)-------------------------------------------------------------------");
        System.out.println();
        test(str2, count);
        System.out.println("^str2:全部存在(大写)-------------------------------------------------------------------");
        System.out.println();
        test(str3, count);
        System.out.println("^str3:部分存在------------------------------------------------------------------------");
        System.out.println();
        test(str4, count);
        System.out.println("^str4:不存在(数字、字符、字母)----------------------------------------------------------");
        System.out.println();
        test(str5, count);
        System.out.println("^str5:不存在(字母)--------------------------------------------------------------------");
        System.out.println();
        test(str6, count);
        System.out.println("^str6:不存在(数字)--------------------------------------------------------------------");
        System.out.println();
        test(str7, count);
        System.out.println("^str7:不存在(字符)--------------------------------------------------------------------");
 
    }
 
    private static void test(String str, int count) {
        str = str.toUpperCase();
        long t = System.currentTimeMillis();
        for (int i = 0; i < count; i++) {
            for (String s : bases) {
                if (str.contains(s)) {
 
                }
            }
        }
        long t2 = System.currentTimeMillis();
        System.out.println(count + "*" + bases.length + " 次 String.contains 耗时:" + (t2 - t) + " ms");
 
        for (int i = 0; i < count; i++) {
            for (String s : bases) {
                if (str.indexOf(s) != -1) {
 
                }
            }
        }
        long t3 = System.currentTimeMillis();
        System.out.println(count + "*" + bases.length + " 次 String.indexOf  耗时:" + (t3 - t2) + " ms");
    }
 
 
}

List.contains和String.contains的区别

如果不把List里的元素遍历出来再用contains过滤关键字，直接用List.contains其效果其实是底层遍历List会用equals去匹配，效果是严格的判相等的方法。
而String.contains是用数组去截取每段内容轮流匹配，类似于模糊查询的效果。